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. 

21 Beloved, if our heart does not condemn us, we have confidence before God; and  whatever we ask we receive from him, 22 because we keep his commandments and do what pleases him. 

23 And this is his commandment, that we believe in the name of his Son Jesus Christ and  love one another, just as he has commanded us. Whoever keeps his commandments abides in God, and God in him. 24 And by this we know that he abides in us, by the Spirit whom he has given us. 1 John 3:19-24 (English Standard Version)

Christians can, and do, have doubts about whether they are truly saved or not. It's not meant to be like that, but it happens. We see in today's reading that it happened even in the days when John wrote his letters. What does John say our hearts can do to us, and what we then need to do to our hearts? (vs 19-20)

He speaks of our hearts condemning us. Could that perhaps be when conscience reminds us of our sins in the past, and even of failures since coming to Christ? John says that when that happens we need to 'reassure' our hearts. How do we go about doing that? What's the first thing to remember in vs 20?

God is far more well informed than even our own hearts. He knows more about us than we do. We only see our sins on the surface – God knows the motives from which those sins sprang. But even then, in Jesus Christ His beloved Son, God dealt with our sins and forgave us fully. Our salvation never has, and never will, depend on how perfect we are. It will always be due solely to God's loving kindness and mercy. He knows our hearts fully – and He loves us still. What will the result be of reminding ourselves of this amazing grace of God? (vs 21-22)

It will lead to having confidence to come boldly to Him with our prayers and requests. That's how the writer of the New Testament letter called Hebrews put it. He said: ”Since we have a great high priest who has passed through the heavens, Jesus, the Son of God, let us hold fast our confession! For we don't have a high priest who is unable to sympathize with our weaknesses, but one who in every respect has been  tempted as we are, yet without sin. Let us then with confidence draw near to the throne of grace, that we may receive mercy and find grace to help in time of need.” (Hebrews 4:14-16)

This doesn't mean that there isn't any responsibility on our part to guard our hearts. What did John say in vs 22, which he then develops in vs 23?

Not only must we believe in the name of the Lord Jesus Christ, i.e. that He is the Son of God and the only name by which there is salvation, but we must put His commandment to love our brothers and sisters in Christ into action. In the verse just before today's reading John had said “let us not love in word or talk - but in deed and in truth.” The commandments 'don't steal, don't lie, don't covet, don't commit adultery, honour your parents', are all summed up and fulfilled when we seek to love one another in the way Christ has loved us. Yes, we will still fall short in all this, but God, who knows everything, also knows that this is what we are seeking to do. This is what abiding in God involves. What is the outcome of such abiding? (vs 24)

The Holy Spirit will bear witness with our spirit that we are a son or daughter of God. God's Spirit will reassure our hearts of God's amazing grace. He will lift up the Lord Jesus Christ in our thoughts and affections. Jesus said: “This is the will of Him who sent me, that I should lose nothing of all that He has given me, but raise it up on the last day. For this is the will of my Father, that everyone who looks on the Son and believes in Him should have eternal life, and I will raise him up on the last day.” (John 6:39-40)