The Diligence of Faith

This is an excerpt from a sermon by John Piper on assurance:

What shall we do? How shall we know and enjoy and be assured of our eternal security? [Hebrews chapter 3, ] verses 12 and 13 give two answers: one more general and the other more specific.

First the general answer in verse 12: "Take care, brethren, lest there should be in any one of you an evil, unbelieving heart, in falling away from the living God." The general answer is, "Take care!" or "Take heed!" or "Look!" In other words, don't be careless or nonchalant or inattentive about the condition of your heart. Look at it. As Paul says in 2 Corinthians 13:5, test yourselves to see if you are in the faith. ...

Someone may ask, "Well, if I am a true partaker of Christ, as I believe I am, why do I have to take heed and be so vigilant, when you have said that I am eternally secure and can't lose my standing in Christ?" I think the question assumes something that the New Testament says is not true. It assumes that God's way for his chosen ones to get to heaven is without vigilance and watchfulness and self-assessment and diligent use of means. But in fact Jesus says, in Luke 13:24, "Strive to enter by the narrow door; for many, I tell you, will seek to enter and will not be able." And Peter says, "Be sober, be watchful, your adversary the devil prowls around like a roaring lion seeking someone to devour" (1 Peter 5:8). The truth is not that true Christians don't have to be vigilant and watchful over their hearts; but that you can know you are a true Christian if you are vigilant and watchful over your heart.

It's the cavalier Christians who need to be worried about their standing. It's those who were baptized and walked an aisle or prayed a prayer and took communion and came to church, but do not love Jesus or count him their dearest treasure or bank their hope on him and look forward to seeing him and can say, "To live is Christ and to die is gain." These are the self-assured ones who need to feel insecure (see Deuteronomy 29:19). ...

That's the first answer to how we stay assured of our eternal security: Take heed to your heart. Guard against unbelief. That is, be vigilant to maintain your confidence and hope in Christ against all competing treasures.

The second answer is more specific in verse 13: "But encourage [or exhort] one another day after day, as long as it is still called 'Today,' lest any one of you be hardened by the deceitfulness of sin." The second answer is that eternal security is a community project. What shall we do at Bethlehem to avoid an "evil heart of unbelief" and not be hardened by the deceitfulness of the sins that tempt us every day to treasure them more than we treasure Jesus?

The answer is that we must be the church for each other. And what is the main thing that the church does for each other? We speak to each other in ways that help us not be deceived by the allurements of sin. Or to put it positively, we speak to each other in ways that cause us to have hearts of faith in the superior value of Christ over all things. We fight to maintain each other's faith, by speaking words that point people to the truth and value of Jesus. That's how you guard against an evil heart of unbelief. Unbelief means failing to rest in Jesus as your greatest treasure. So helping each other believe means showing people reasons why Jesus is more to be desired and trusted and loved than anything else.