NET
10 By this the children of God and the children of the devil are revealed: Everyone who does not practice righteousness—the one who does not love his fellow Christian—is not of God.
Darby
10 In this are manifest the children of God and the children of the devil. Whoever does not practise righteousness is not of God, and he who does not love his brother.
KJV
10 In this the children of God are manifest, and the children of the devil: whosoever doeth not righteousness is not of God, neither he that loveth not his brother.