Genesis 4:9 - Joseph Benson’s Commentary on the Old and New Testaments

Where is Abel thy brother? Not that God was ignorant where he was, but he asks him that he might convince him of his crime, and bring him to a confession of it; for those that would be justified before God, must accuse themselves. And he said, I know not Thus in Cain, the devil was both a murderer and a liar from the beginning. Am I my brother's keeper? Is he so young that he needs a guardian? Or didst thou assign any such office to me? Surely he is old enough to take care of himself, nor did I ever take charge of him.