But Pharaoh's heart was hardened, and God spake to Moses, saying, "This wicked fellow remains hard of heart, in spite of the three plagues. The fourth shall be much worse than those which have preceded it. Go to him, therefore, and warn him, it would be well for him to let My people go, that the plague come not upon him."
The fourth plague was also announced to the king early in the morning by the river's brink. Pharaoh went thither regularly, for he was one of the magi, who need water for their enchantments. Moses' daily morning visits were beginning to annoy him, and he left the house early, in the hope of circumventing his monitor. But God, who knows the thoughts of man, sent Moses to Pharaoh at the very moment of his going forth.