Everyone who commits sin is a child of the devil; for the devil has been sinning from the beginning. The Son of God was revealed for this purpose, to destroy the works of the devil.
Those who have been born of God do not sin, because God's seed abides in them; they cannot sin, because they have been born of God.
References for 1 John 3:9
The 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.
References for 1 John 3:10