3 The way we may be sure that we know him is to keep his commandments.
4 Whoever says, “I know him,” but does not keep his commandments is a liar, and the truth is not in him.
5 But whoever keeps his word, the love of God is truly perfected in him. This is the way we may know that we are in union with him:
6 whoever claims to abide in him ought to live [just] as he lived.
7 Beloved, I am writing no new commandment to you but an old commandment that you had from the beginning. The old commandment is the word that you have heard.
8 And yet I do write a new commandment to you, which holds true in him and among you, for the darkness is passing away, and the true light is already shining.
9 Whoever says he is in the light, yet hates his brother, is still in the darkness.