Unbelief is like a spiritual disease we must constantly fight with mutual exhortation.


Hebrews 3:7-19

Hebrews 1-8 (WBC)William Lane

Hebrews: Evangelical Biblical Theology Commentary, Thomas Schreiner


Sermon Transcript

We have some members of the church here who are diabetic, and so I’ve come to learn that there are various ways for people with type 1 diabetes to get the insulin they need. But I remember at a young age seeing my cousin’s husband inject himself in the stomach with a shot of insulin. As a young kid I was naturally curious, and was surprised to learn that he actually repeated that ritual every day, and sometimes even more than once per day. He knew he had a disease, and if he let that disease run its course in his body, it could kill him. So he learned to live with that constant awareness, and to administer to himself the proper medication against it every day. In the passage on which we are focusing today in the book of Hebrews, we will see there is also what we could call a spiritual disease inside each of us: Unbelief. It is that force in us that inclines us, when we hear God’s word, to ignore it, doubt it, or rebel against it. When someone becomes a Christian, it is because God has subdued that force in them. One of the ways we even refer to Christians is as “believers”; to be a Christian is to be one who believes God’s word of salvation. And yet, we see in this text that the disease of unbelief, while dethroned in our hearts, is not yet eliminated from our system. And therefore, like my cousin’s husband in his battle against diabetes, we too must be alert, and fight against unbelief every day, not with insulin, but with exhortation. So constantly exhort one another away from unbelief, because unbelief is powerful, and unbelief is perilous.


Unbelief is powerful


Our text begins in verse 7 with a “therefore”, once again connecting it to what came before, as we have seen so often already in Hebrews. The verse immediately before it concluded with this idea that we who are believing in Jesus are God’s house, God’s people, God’s family, but then it added a condition: We are his house only if we hold fast our confidence and our boasting in our hope. Therefore, now the author says in verse 7, as the Holy Spirit says, “Today, if you hear his voice, do not harden your hearts as in the rebellion.” In other words, since we are only God’s people if we continue believing God’s word, today, if you hear it, do not harden your heart against it.


The passage our author quotes in verses 7-11 comes from Psalm 95, but notice how he introduces it: “as the Holy Spirit says”. Now all he’s doing is quoting a passage from the Bible, and yet he can say, present tense, that what was written in the Bible hundreds of years prior to him, in a different language originally, is what the Holy Spirit says in his day. How can he say that? He can say that because the words of scripture are the words of God. Though they were written by human authors, those authors wrote what God the Holy Spirit led them to write, so that the final product, what ends up written in scripture, is not only their word, but God’s Word, and as God’s Word, it is, as we’ll see in chapter 4, living and active, so that today the Holy Spirit continues to speak these very words. And what he says is, “Today, if you hear his voice, do not harden your hearts as in the rebellion.”


Note the significance, then, of how you respond to God’s voice today. We are God’s people if we hold fast our confidence; in our passage today we see in verse 14 that we have come to share in Christ if we hold our original confidence firm to the end. How can we hold fast our confidence to the end? Start with today, and if today, you hear God’s voice, don’t harden your heart. This is true of any long-term goal, right? If you want to lose 50 pounds, you probably realize you can’t lose it all today. But today, you can choose to eat healthy and exercise. Then once tomorrow is today, you do that again, and so on. So also, if you want to make it from grace to glory, if you want to reach your heavenly home, start with today, and today, if you hear God’s voice, do not harden your heart.


Now many evangelicals today, when they read that phrase “today, if you hear his voice, do not harden your heart” are prone to interpret it as meaning “today, if you get a strong internal feeling about something, follow it as though it is God’s voice.” That’s not what verse 7 means. Remember that the author of Hebrews has already quoted scripture as what the Holy Spirit is saying today. Remember also that the author of Hebrews said in chapter 1 that God has spoken to us in these last days by his Son (1:2), and the way that speech got to them was that first Jesus himself spoke it, and then those who heard Jesus spoke it to the Hebrews (2:3-4). So some of what the author is saying to his audience is that you have already heard God’s voice when the message Jesus declared was declared to you by those who heard it. So he already said in chapter 2 that we must pay much closer attention to what we have heard (2:1), and he goes on to say in chapter 4 that good news has already come to us (4:2). And, as the message declared by Jesus is also God’s Word, it too remains living and active.


So, how then do you hear God’s voice today? You hear God’s voice today when the Bible is read aloud, rightly explained, and rightly applied. The Holy Spirit says today what he said in the Old Testament, and in the New Testament we have the attestation of those who heard the message declared by Jesus, so that all of it together, what we now call the Bible, is the living and active word of God, through which the Holy Spirit still speaks today. Today, if you hear the Bible read aloud, do not harden your heart. Today, if you hear the Bible rightly explained and applied, do not harden your heart. Do you listen to the reading of the Bible aloud as though you are hearing in it the very voice of God? How do you listen to the preaching of God’s Word? How do you listen to the biblical counsel of a pastor or another church member?


Here we’re told how not to listen to it: Do not harden your hearts. You probably know what it’s like to harden you heart. If you are a pessimist, and you hear someone telling you that if you just do these 3 things, your wealth will grow, you harden your heart against that. If you are an optimist, and you hear someone telling you no matter what you do, your wealth will not grow, you harden your heart against that. What the Holy Spirit is telling you is that if you hear God’s voice, don’t do that! When you hear scripture read aloud, rightly explained, and rightly applied, don’t look for ways to explain it away. When scripture issues a warning, don’t just tell yourself it doesn’t apply to you. When scripture issues commands, don’t get to work finding a way to justify not obeying it. When scripture issues a promise, don’t go looking for reasons it’s unlikely to be fulfilled. When scripture issues a word of comfort, don’t refuse to receive it. Today, if you hear his voice, do not harden your heart. Take God at his word. If God says it, believe it.


And the reason the Holy Spirit must say this to us is because it is so not automatic. Unbelief is powerful. It is so easy to harden your heart, and if today you harden your heart, tomorrow you will find it easier to harden it further. We know that because that’s what the fathers of the Jewish people did in the wilderness. Verses 8-11, again quoting Psalm 95, recount that story. Let me give you a bit of the background: God’s people were enslaved in Egypt, but God led them out of slavery in Egypt through a man God appointed to be their leader named Moses by first sending 10 miraculous plagues on Egypt, then parting a sea so that they walked through it on dry ground, after which time God brought the waters back on their enemies to drown them. After Moses led them out, God spoke to them at Mt. Sinai, where he gave them his law accompanied by fire, smoke, and thunder on top of the mountain. They heard his voice there in a way many of us would consider more believable than the way we hear God’s voice through human messengers. After giving them his law, he told them to leave Mt. Sinai and to go take possession of the land that the LORD had sworn to give to their fathers (Deut 1:6-8). So Moses began leading them toward that land, and during that time they again witnessed God’s work in providing for them: He made water flow from a rock, he rained down bread from heaven, and he himself led them in a cloud by day and a pillar of fire by night. So if there was anyone we might assume would have a really easy time believing God’s word, it had to be them. And yet, they didn’t. When they got close to the land of which they were to take possession, they sent spies to scope it out, and all but two of the spies brought back a negative report of the land. They said it was a good land, but the people in it were too powerful and numerous for them to take it. The unbelief of those ten spies spread like wildfire, and the people decided not to enter the land as a result. Instead, they grumbled against Moses and even said they wanted to go back to Egypt. God took this as rebellion against him, as Moses was the leader God appointed and God was the one who commanded them to go take the land in the first place. Though it was God’s own voice that told them to go in and take this land, on that day, the day here called the rebellion and the day of testing in the wilderness, the people of Israel hardened their hearts.


Now, if that kind of unbelief was possible for them, do you really think it’s impossible for you? Don’t think that way. Instead, verse 12: Take care, brothers and sisters, lest there be in any of you an evil, unbelieving heart, leading you to fall away from the living God. Don’t hear the story of Isreal and think, “Welp; that’ll never be me”. Hear the story of Israel and think: “Wow; that could be me!” Take care that it not be you. That command there “take care” could also be translated “watch out”. Be on high alert. Unbelief is powerful! Many of us in this room have not felt much need in our lives to be on high alert against a powerful, imminent threat, but can you imagine what it might have been like to be a Ukrainian citizen living in Kherson in early March of last year when Russia began invading it? You probably wouldn’t have felt like you could go just wake up the next day, do some yoga, eat breakfast, brush your teeth, grab a shower, get dressed, head off to work, come home, eat dinner, watch some TV, and go to bed, because you faced a real, imminent threat. Perhaps in small ways you’ve even felt something like that in Philadelphia: You have an uncomfortable interaction, you get a Citizens app alert, you hear about violent crime, and you think: I’d better lock my door; maybe I shouldn’t walk there alone at night; maybe I should even get an alarm system. The more likely you think the event is to happen, the higher your alert level. Well, what this text is showing us is that unbelief is very much possible. If an evil, unbelieving heart could develop in the people who heard God’s voice and saw his works for 40 years in the wilderness, it can develop in you and me. It’s that powerful. I wish that wasn’t the case; it doesn’t feel good to be on high alert. It must not have felt good to be in Kherson as Russia invaded, but it would have done the Ukrainian citizens no good to simply pretend the attack was not happening so that they could avoid the discomfort of being on high alert. So also, it will do you no good to pretend you are somehow above an evil, unbelieving heart to avoid the discomfort of being on high alert.


We can safely assume the high alert the Ukrainian citizens felt was not only for their own sake, but for the sake of their neighbors as well. So also here, notice in verse 12 that we are commanded to take care, not only that there not be in us an evil, unbelieving heart, but that there not be in any of you an evil, unbelieving heart. Be on high alert for yourself because unbelief is possible for you, but be on high alert for your fellow church members as well, because unbelief is possible for them. That concern for ourselves and for one another in the face of the threat of developing an evil, unbelieving heart that would lead us to fall away from the living God then leads in to the command of verse 13: But exhort one another every day, as long as it is called today, that none of you may be hardened by the deceitfulness of sin. Notice again, the goal is not just that you not be hardened by the deceitfulness of sin, but that none of you be hardened by the deceitfulness of sin. Churches often talk about their goals or visions: Baptize a certain number of people, plant a certain number of churches, send a certain number of missionaries. But how’s this for a goal? Every one of us makes it to heaven. We have 97 members currently; how’s this for a goal? All 97 of us make it to heaven. Not a single one of us develops an evil, unbelieving heart, leading us to fall away from the living God. Not a single one of us is hardened by the deceitfulness of sin. Could you get on board with that goal? Does that seem like a goal worthy of your time and energy? Certainly that’s not the only goal of a church, but it is held out to us here as a worthwhile one.


And here’s the question verse 13 answers: If we are to be on high alert that there not be in any of us an evil, unbelieving heart, what are we to do with that? If you’re on high alert against an invading nation, you either flee, or you prepare to fight back. If you’re on high alert against crime in your neighborhood, you lock your doors, you get an alarm system, maybe you even move to another neighborhood. Against this enemy though, the enemy of unbelief, fleeing won’t work: Notice in verse 12 that unbelief develops in our hearts, and you can’t flee from your own heart. No matter where you go, you will still be there.


So, what can you do? You can’t flee, but you can fight unbelief by exhorting one another every day. Interesting, isn’t it, that the way to fight unbelief is not by something you can do by yourself? God doesn’t merely tell you to fight unbelief by taking your thoughts captive, reading your Bible alone, journaling alone, and praying alone, valuable as those things are. Perhaps it’s stating the obvious, but to exhort one another you need another to exhort, and another to exhort you. This is one of the reasons God calls us to join a church: That we might exhort one another. If you refuse to join a church or even if you join a church and simply refuse to really engage with the people in it, you aren’t just robbing yourself of the exhortation you need; you are rοbbing others of the exhortation they need! The word there translated “exhort” is hard to translate into English. It means something like encourage, but we tend to think of encouragement as purely affirmative, whereas this word can also include words that challenge us. If you think of the scene we mentioned earlier of Israel on the brink of the promised land, exhortation there would have sounded something like, “Yes, the people in the land are stronger than we are, but the LORD is on our side, and they are not stronger than he. I know you are afraid, but let’s trust the LORD and go take the land,” and not as much like “You can do it! Those people in the land got nothing on you! You’re stronger than you ever dreamed!” nor as much like “Oh man, we better go in. We’ll probably all get killed but God told us we have to go.”


Now, today instead of being on the brink of a promised land here on earth, we look forward to the heavenly city and exhort one another to believe God’s promises so that we might enter it. We exhort one another away from unbelief by exhorting one another to believe God’s Word. How can we do that well? First, let me suggest two things you must know well if you are to exhort one another well. First, you must know the Bible well. You can’t exhort one another to believe God’s Word if you don’t know God’s Word yourself. Study the Bible not only for its application to your own life; study it also so that you actually have something helpful to say to one another. Second, you must know one another’s hearts well. Since unbelief develops in the heart, you must know one another at a heart level if you are to exhort one another in such a way that addresses the unbelief of one another’s hearts. That means to do this well you will have to get beyond conversations about sports, work, and the weather. It generally means you will even have to get beyond conversations about the Bible and theology, insofar as those conversations remain detached from your lives. You have to learn to talk to one another instead of simply talking about things. A simple way to begin doing that is to learn to ask heart-level questions rather than fact-level questions. So, instead of asking, “how was your weekend?” consider asking a question like, “What was the worst part of your weekend? What was the best part?” or “How’s your heart today?” or “How are you seeing God in your life today?” Then, as you get to know one another’s hearts, ask the Holy Spirit to give you wisdom as to what part of scripture would best exhort one another toward our heavenly home, and speak it.


To develop that kind of knowledge of one another, sociologists even recognize that you do typically need a number of regular spaces in which to interact. In our church, we have this gathering every Sunday, and we have Citygroups that meet throughout the week. In addition, we have a weekly pre-service prayer meeting, a monthly prayer service, bi-monthly Sunday seminars, quarterly members’ meetings, and many members of our church are also in smaller groups we call discipleship groups. We don’t always get to know one another’s hearts in those actual meetings, though hopefully in Citygroups and discipleship groups more of that is happening, but each of them creates another context in which we can interact with one another, and the hope is that from that, deeper relationships can form in which we know one another’s hearts. And I will say after 8 years here, I have observed that those who simply make it a point to be at those things regularly, tend, in general, to have more heart-level relationships in which this kind of mutual exhortation happens regularly.


But it does require intentionality and willingness. It requires intentionality to order your schedule in such a way as to be around one another. It requires intentionality to be around one another in contexts where heart-level conversations can happen. It requires a willingness to push through the comfortable conversations to know someone else’s heart, and it requires a willingness to let others know your heart. That is hard work, and again, in my experience, it typically does feel effortful, especially on the front end. But, brothers and sisters, unbelief is powerful! It’s so powerful that verse 13 tells us to exhort one another every day, as long as it is called “today”. That means until we reach the world that is to come, our heavenly home, you need this kind of exhortation constantly from your brothers and sisters, and your brothers and sisters constantly need this kind of exhortation from you. Keep both of those in mind as you exhort one another. Sometimes you can seek relationships with others because you know you need to be exhorted, but that can easily transform the relationship into something selfish, where you only engage to the extent you feel you need what someone else is offering. On the other hand, sometimes you can seek relationships with others because you feel you have so much to offer them, but that can easily cultivate pride in you and a neglect of your own temptation toward an evil, unbelieving heart. That’s the wisdom of these “one another” commands: They’re reciprocal. You need the exhortation of your brothers and sisters, and your brothers and sisters need your exhortation.


And why wouldn’t it suffice for you to just guard yourself from an evil, unbelieving heart by yourself? Because, as verse 13 continues, if we don’t exhort one another, we are prone to be hardened by the deceitfulness of sin. The hardening of your heart isn’t just something you consciously choose to do, in other words. There is actually a force at work in you, called sin, and the way it operates is by deception. It doesn’t hold up a flashing, neon sign that says, “Hey, there’s God’s Word. Don’t believe it! Believe what I’m telling you instead!” It sounds more like, “Ok, there’s God’s Word. But did he really say…?” and it is just so easy to be deceived by that, which means by its very nature, you don’t know you’re being deceived! And so, God has given you others, who can look at you with a greater measure of objectivity and say, “Hey, here’s what’s true”. I think of times recently when I’ve been despairing over decisions I’ve made, and I kinda know in my head that I should believe that ultimately, I am where I am because this is where the Lord has me, but it’s been so much easier for me to believe it when brothers and sisters in Christ have just told me, “But Mike, you are where you are because that’s where the Lord has you.”


Here’s how Dietrich Bonhoeffer described that reality: “God has willed that we should seek and find His living Word in the witness of a brother, in the mouth of man. Therefore, the Christian needs another Christian who speaks God’s Word to him. He needs him again and again when he becomes uncertain and discouraged, for by himself he cannot help himself without belying the truth. He needs his brother man as a bearer and proclaimer of the divine word of salvation. He needs his brother solely because of Jesus Christ. The Christ in his own heart is weaker than the Christ in the word of his brother; his own heart is uncertain, his brother’s is sure.”


Constantly exhort one another away from unbelief because unbelief is powerful. And constantly exhort one another away from unbelief because unbelief is perilous.


Unbelief is perilous


Verse 14 transitions us into this next section of our passage, although the peril of unbelief was already hinted at in verse 12. Where does an evil, unbelieving heart lead? It leads you to fall away from the living God. As in chapter 2 where we saw the language of drifting away from the word, here we see a similar concept in this idea of falling away from the living God. In either case, it’s not a sudden, immediate drop. Here’s how C.S. Lewis described it in his book Screwtape Letters, a book in which he develops letters from an imaginary demon, Screwtape, to his nephew, Wormwood, a demon in training. This is Screwtape, the master demon, speaking to his apprentice, Wormwood: “You will say that these are very small sins; and doubtless, like all young tempters, you are anxious to be able to report spectacular wickedness. But do remember, the only thing that matters is the extent to which you separate the man from the Enemy (that’s God)…Murder is no better than cards if cards can do the trick. Indeed the safest road to Hell is the gradual one—the gentle slope, soft underfoot, without sudden turnings, without milestones, without signposts.”


As you harden your heart today, it’s a little harder tomorrow. Then it’s easier to harden it again. As you distance yourself from your brothers and sisters, sin is in there hardening your heart further with its deceptive power, unchecked by the exhortation of others. As that evil, unbelieving heart is allowed to grow, you fall further and further, until eventually you fall away from the living God entirely. As verse 14 goes on to say, we have come to share in Christ, but only if indeed we hold our original confidence in Christ firm to the end. You starting to see how perilous unbelief is? It leads us to fall away from the living God, and through it, we lose our share in Christ.


Now, I know some of you may be wondering, “Are you saying it’s possible for a true Christian to lose their salvation?” No, I’m not saying that, nor is that what this text is saying. But the author doesn’t know who among those to whom he’s writing is a true Christian, and who is merely professing faith to cover up an unbelieving heart, nor do I as a preacher know that of you all who are here today. Furthermore, even for those who do sincerely believe, these warnings are intended by God as the means through which he keeps you to the end. He tells you watch out, lest there be in any of an evil, unbelieving heart, and then he so works in you as to ensure that you do in fact watch out, and therefore exhort one another every day, and therefore do not end up with an evil, unbelieving heart. But make no mistake about it: You still must watch out, you still must exhort one another with the strength that God provides, and those who do not will fall away from their profession, thus demonstrating that they never truly believed in the first place.


So the author reminds us again of what is said in Psalm 95: Today, if you hear his voice, do not harden your hearts as in the rebellion, and then starting in verse 16 he explains the text even further. He asks first, “Who were those who heard and yet rebelled?” Was it not all those who left Egypt led by Moses? They heard his voice, they saw his wonders, and yet they rebelled. And with whom was God provoked for forty years? Was it not with those who sinned, whose bodies fell in the wilderness? Forbidden from entering the promised land because of their unbelief, that whole generation died in the wilderness. Unbelief was literally deadly in their case. That’s how seriously God takes it.


And then, verse 18, to whom did he swear that they would not enter his rest, but to those who were disobedient? The fact that those who disobeyed God’s command to enter the land were destined to die wasn’t even the worst part of the curse. The worst part was God’s sworn oath that they would now not be allowed to enter his rest. The idea is that the promised land was meant to be a place of rest for God’s people. Finally, after over 400 years of slavery in Egypt, God delivered them miraculously and promised to give them rest. But, because they disobeyed his command to take the land, God swore that they would not enter his rest. In fact, even in Numbers 14 we read that they tried to enter the land after all, and they were defeated, because the LORD had already sworn that they would not enter his rest. So our author concludes in verse 19 that what we learn from this is that they were unable to enter because of unbelief. They disobeyed God’s command to enter the land because they did not believe God’s promise to give them the land, despite the powerful enemies they could see in front of them.


Yet even that land was not intended by God to be the place of ultimate rest for God’s people. That land was a type, a shadow, of a heavenly realm of rest, and it is into that heavenly realm that Jesus has now entered. Moses couldn’t lead the people into that rest, and just like the people of Israel, we cannot enter that rest on our own. We too have heard God’s Word, and hardened our hearts to it. How many times have we heard the Bible clearly read, explained, and applied and have yet ignored it, explained it away, or actively rebelled against it? How many of his commands have we disobeyed because we’ve simply refused to believe that what he says is true? I get it, you’ve got intellectual doubts; I do too. But beneath those, don’t you also find an unbelieving heart? Don’t you find some part of you that just doesn’t want God to be God, that just doesn’t want to trust any voice outside your own, that just doesn’t want anyone to be in control of you but you? I know I find that in me. It’s powerful. No matter what God says, no matter how believable it is, we look for and inevitably find a reason to doubt it because we too are sinners, unworthy to enter God’s rest. And yet, God, in his grace, has provided a way for us to enter his rest, not by ourselves and our own efforts. If you try to enter God’s rest by your efforts to improve yourself, you’ll be as unsuccessful as Israel was when they tried to enter the land after all, after they’d already disobeyed. That ship has sailed. Now the only way in is through the one who obeyed perfectly. When Jesus Christ became man, he knew the only way for him to enter God’s rest would be by fighting against the greatest enemy of all: Death itself. Yet he so believed God’s promise that he willingly suffered death on our behalf, taking upon himself the punishment for all the unbelief of all who would ever turn from their unbelief and believe in him, and indeed, from death itself God brought him to life, and he has entered into God’s rest on our behalf. If you are here today and you are not believing in him, turn from your unbelief, believe in him, and through him, you will enter God’s rest.


To you who do believe today, be on high alert against unbelief. To be on high alert about something we have to believe that the threat is both real and perilous. Nuclear attacks are perilous, but they aren’t very likely to happen to us, so most of us do not live our lives on high alert against them. It’s very likely that if you park your car on the street in Philadelphia, your bumper will get tapped by a neighboring car, but it’s not that perilous, so most of us do not live on high alert against it. But unbelief is powerful; it can happen to you! An evil, unbelieving heart developed in those who saw God send plagues on Egypt and part the Red Sea, who heard God’s voice at Sinai, who drank water from a rock and ate bread from heaven. You think you’re immune? You aren’t. The command of verse 12 to be alert is addressed to brothers and sisters, to believers in Jesus. The threat of unbelief is real, and it’s perilous. The consequence is falling away from the living God, losing your share in Christ, and therefore failing to enter God’s heavenly rest. To summarize it with one word, the consequence is hell. That’s how perilous unbelief is.


And yet, we have such good news with which to fight it! In these last days God has spoken to us by his Son. He has suffered on our behalf, he has entered God’s rest on our behalf, he is able to help those who are now being tempted, and we have come to share in him! Be on high alert, but don’t panic. Rather, use the living and active word of God that he has spoken to us in these last days by his Son, and that he has committed to writing in the Bible, to exhort one another constantly.