1 John 3:19-20, “19 By this we shall know that we are of the truth and reassure our heart before him; 20 for whenever our heart condemns us, God is greater than our heart, and he knows everything.”
“Doubt” is the perfect word to character my young, Christian faith. Before I was saved, I lived as a false convert, continually haunted by doubts of my salvation—which in turn led me to strive to keep my favored standing before God with works. When I became a Christian and recognized that salvation is by faith alone because of God’s grace, I still struggled with doubt. My legalistic ways were difficult to let go of. I doubted that God could truly love a wretch like me, and could continue to love me despite my sin.
1 John came as a healing balm to my doubt during that first year of my Christian walk, and these verses were my comfort:
“By this we shall know that we are of the truth and reassure our heart before him; for whenever our heart condemns us, God is greater than our heart, and he knows everything” (1 John 3:19-20 ESV).
If you feel like you are wasting away in sorrowful doubt, I hope that these verses can bring you the assurance they brought me, as we examine the proof and basis for our salvation, and discover how to assure our hearts when they condemn us.
The Fruit and Proof of Our Salvation (v. 19)
1 John as a whole was written for those who struggle with assurance of faith. John wrote near the end of the epistle, “I write these things to you who believe in the name of the Son of God, that you may know that you have eternal life” (1 John 5:13). It is like a series of tests for the Christian to examine himself with to see if they are truly of the faith. It’s not that any of these actions save us, but rather they are the fruit that is produced because we are saved. They give evidence of our salvation.
Verse 19 begins with “By this,” taking us back to the previous passages. The tests of this chapter are continual obedience (vv. 4-10) and love for fellow believers (vv. 11-16). In this chapter, John has already established that true believers will not make a practice of sin but of repentance and righteousness. This isn’t to say we will never sin (I’m sure each of us can attest to this today) because John himself says that if any of us declares we are without sin the truth is not in us (1 John 1:10). Rather, the believer is striving to be obedient and put off sin. Their love for God has fueled them to pursue righteousness and throw away every sin. The question is, “Is your life presently characterized by sin or righteousness?”
The second test in this chapter is love for believers. Ask yourselves the following two questions, “Do you truly love others? Or do you hate them?” John writes that those who hate are murderers, and murderers do not have eternal life abiding in them (1 John 3:15). Conversely, believers love one another, with not words alone but also with truth and deed (1 John 3:18). Christians see each other in need, and they seek to help (1 John 3:17). Believers love one another—even the difficult people—with a love so strong that they would lay down their lives for one another (1 John 3:16). Friend, are you characterized by Christ-like love for your brothers and sisters in Christ, or are you characterized by the same murderous hate as Cain (1 John 3:11-12)?
It is by these tests that we know whether or not we are abiding in Christ as believers. When the guilt and doubt press down on us, we can examine our lives and see if the gospel has truly changed us. Someone who has the Holy Spirit living inside of them, who has been saved by the grace of God, and who has experienced the love of Christ should be different from the world. They should not love and pursue sin as the world does but daily strive for righteousness. They should not be filled with hate and murder, but with love and goodness towards others.
If we and other Christians see these characteristics of righteousness and love in our lives, we can be assured that we are believers. As those who doubt, we know the stench of our sin and wretchedness. We know our inability to do anything pleasing to God. Therefore, if we have obedience and love in our lives, that is a sign that the Holy Spirit dwells in us. And we can rejoice in the Lord in that.
When Our Hearts Condemn Us (v. 20)
Ultimately, the basis for our assurance can only come from God. Our hearts are deceitful and desperately sick (Jeremiah 17:9), so they cannot be trusted. These doubts will continue to bash you, even though you are truly saved. In those moments when our heart condemns us, we can’t look to our hearts for assurance. We need to look to something bigger, something much grander than ourselves. We must look to God.
John MacArthur wrote, “God knows those who are truly his (2 Tim. 2:19) and wants to assure his own of their salvation. Although Christians may have insecurities and doubts about salvation, God does not condemn them (Rom. 8:1).” God is the One who will ultimately justify or condemn you, not your fickle heart.
If you have believed in the Lord Jesus Christ for salvation and confessed him with your mouth as Lord, then you are saved (Romans 10:9). Trust God and what he has declared about your salvation, not your heart. “When our hearts condemn us, God’s promise to receive the repentant and humble person who trusts in Jesus alone (John 6:37–40) is the ultimate source of our assurance.”
Relying on God’s Word, Not Our Feelings
As believers, even strong believers, we can battle doubts of salvation. It doesn’t make us any less saved, or any less of a Christian. But in those moments, we must learn to not trust our hearts that condemn us but to trust God’s Word. God’s Word gives us the assurance we need for salvation.
Don’t look to a date on the calendar, a prayer you prayed, or the kind words of another. Look to see what Scripture says. Hold yourself against it, not anyone else. See if you show the fruits of a true believer—repentance, righteousness, and love. See if you have obeyed God’s call to salvation—to believe, turn from your sins, and trust the Lord. If so, you can know with assurance that God’s grace shines on you, and he has brought you from death to life. And though your heart still may condemn you, turn to God, who is greater than your heart.
 John MacArthur, The MacArthur Bible Commentary (Nashville, Tennessee: Thomas Nelson, 2005), 1962.
 “God Is Greater,” Ligonier Ministries, , accessed May 9, 2018, https://www.ligonier.org/learn/devotionals/god-greater/.