In this the children of God and the children of the devil are manifest: Whoever does not practice righteousness is not of God, nor is he who does not love his brother.
1 John 3:10
Surrounding context
3:9 Whoever has been born of God does not sin, for His seed remains in him; and he cannot sin, because he has been born of God.
3:10 In this the children of God and the children of the devil are manifest: Whoever does not practice righteousness is not of God, nor is he who does not love his brother.
3:11 For this is the message that you heard from the beginning, that we should love one another,