The apostle John thought it was important for us to tell the difference between a child of God and a child of the devil. After all, we must lay down our lives for the least of Christ's brethren. That means, if necessary, we share our food, our clothing, and our homes with them. For our protection, he gave us this clear outline of the evidence we should look for in ourselves and others:
"1Jn 3:8 He that committeth sin is of the devil; for the devil sinneth from the beginning. For this purpose the Son of God was manifested, that he might destroy the works of the devil.
1Jn 3:9 Whosoever is born of God doth not commit sin; for his seed remaineth in him: and he cannot sin, because he is born of God.
1Jn 3:10 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."