World Wide Study Bible
a Bible passage
10The children of God and the children of the devil are revealed in this way: all who do not do what is right are not from God, nor are those who do not love their brothers and sisters.
doeth not righteousness—Contrast 1Jo 2:29.
he that loveth not his brother—(1Jo 4:8); a particular instance of that love which is the sum and fulfilment of all righteousness, and the token (not loud professions, or even seemingly good works) that distinguishes God's children from the devil's.