Exodus 8:15

But when Pharaoh saw that there was respite, there was relief from the pressure of the plague and he could once more get his breath, he hardened his heart and hearkened not unto them; as the Lord had said. Thus it happens even in our days that obstinate sinners will cry for help when the hand of God rests heavily upon them. But there is no real change of heart in their case, and as soon as they feel relief, they forget all their solemn promises.