Everyone who has this hope set on him purifies himself, even as he is pure.

 3:10-18 In this the children of God and the children of the devil are made plain; anyone who does not do righteousness is not of God, and neither is he who does not love his brother, because the message that we have heard from the beginning is the message that we should love one another, that we should not be like Cain, who was of the Evil One and slew his brother. And why did he slay him? Because his works were evil and his brother's works were just. Do not be surprised, brothers, if the world hates you. We know that we have passed from death to life, because we love the brothers. He who does not love remains in death. Anyone who hates his brother is a murderer. He does not possess eternal life abiding within him. In this we recognize his love, that he laid down his life for us; and we ought to lay down our life for the brothers. Whoever possesses enough for his livelihood in this world and sees his brother in need and shuts his heart against him, how does the love of God abide in him? My dear children, do not make love a matter of talking and of the tongue, but love in deed and in truth. 