Is the heart some private, inner room, in which we can conduct ourselves in secret, away from the eyes of man and of God? Can we obey the commandments at the external level, and no one know that we also break them in another place where we think that no one can see? Can we successfully hide our hypocrisy? We can be away from the eyes of man, yes, but not of God. Purity of heart is what God requires, and if anything the real person is what goes on in the heart, not what goes on in the outward man.