Ambrose of Milan : But Pharaoh, who was devoted to beliefs and vain superstitions (Egypt being filled with frogs, which produced empty sounds and noisy clamor), when Moses said to him: 'Appoint a time for me to pray for you, and for your servants, and for your people, so that the Lord may exterminate the frogs' (Exod. VIII, 9); though he should have been compelled by such great necessity to pray, and not delay any longer, he replied: 'Tomorrow'; idle and negligent, intending to destroy Egypt by incurring the punishment of delay. And so, when he obtained these things, he became ungrateful; and being lifted up in his mind with his flesh, he forgot God. — On Cain and Abel 1.9.33