“And by this we know that we are of the truth, and shall assure our hearts before Him.” (1 John 3:19, NKJV) 

DNA tests are all the rage nowadays. They have been used to overturn false convictions and to lead to actual culprits. They are also common in determining paternity, which can be very important in considering inheritance and other benefits. 

John presents us with a Paternity test of sorts when he helps us to know if we are of the truth, and have assurance of the blessings of salvation. Have we been born again into the family of God? Are we heirs of eternal life? 

Truth is a prominent theme in John’s writings. It speaks to what is of God and stands in contrast to the lies of the devil. In his first epistle John speaks of practicing the truth (1:6), of the truth being in us (1:8; 2:4), of knowing the truth (2:21), of our being of the truth (3:19), and the Spirit of truth (4:6; 5:6). Truth relates to our regenerated heart and gospel hope. It directs our steps. 

Assurance of salvation proceeds from authenticity of regeneration. The Spirit bears witness with our spirit that we children of God and so heirs of eternal life. If the truth is in us, it defines us, compels us, directs us, convicts us, and comforts us. 

John explains how the truth now essential to our new being in Christ shows up in us. “For if our heart condemns us, God is greater than our heart, and knows all things. Beloved, if our heart does not condemn us, we have confidence toward God” (1 John 3:20–21). 

John seems to giving us a mixed message, but in actuality he is bringing to bear what he has taught earlier. If we are of the truth, our heart will condemn us of our sin. “If we say that we have no sin, we deceive ourselves, and the truth is not in us” (1 John 1:8). But the truth of the gospel is that Christ atoned for our sin (1 John 2:1-2) and there is now no condemnation through faith in Him. God, who is greater than our heart, sees the sin by which our heart condemns us but also sees His Son who made an end of our sin. 

It is in Christ – the way, the truth, and the life – that we have confidence before God, and that we come before Him to ask with thanksgiving and great expectation. “And whatever we ask we receive from Him, because we keep His commandments and do those things that are pleasing in His sight” (1 John 3:22; cf. Heb. 4:16). 

Keeping God’s commandments is not the basis for our assurance or the price of admission to His presence. Rather, obedience with an eye to pleasing God is a character trait of our new DNA in being born again. 

How can we reassure our heart troubled by sin?