  One plausible answer might be that God's perfect knowledge of right and wrong, or God's own moral perfection, explains why his commands serve legitimately as standards for us. But that answer assumes that standards of morality exist independently of God's will (either as objects of his knowledge or as standards in light of which He counts as morally perfect), in which case speaking of morality as consisting of God's commands will not explain the origin or nature of these independently existing standards. 