He questioned him because He did not want Cain to perish. God wanted Cain to repent of his sins, and follow the right way. God was warning Cain about a terrible enemy, which threatened to destroy him and his descendants. Sin is the problem of the world . It is our worst enemy.
Sin is like a snake, full of deadly poison.
It is like a little spark that can burn up a great forest. Sin is lawlessness . He who does what is sinful is of the devil, because the devil has been sinning from the beginning. Sin is the force that moves in the members of our bodies and fights against what is true and good. Sin is anything that does not agree with the will of God.