Exodus 8:23-25

And I will put a division between my people and thy people: to morrow shall this sign be. {a division: Heb. a redemption} {to morrow: or, by to morrow} And the LORD did so; and there came a grievous swarm {of flies} into the house of Pharaoh, and {into} his servants' houses, and into all the land of Egypt: the land was corrupted by reason of the swarm {of flies}. {corrupted: or, destroyed} And Pharaoh called for Moses and for Aaron, and said, Go ye, sacrifice to your God in the land.