Exodus 8:23 in the King James Version
And I will put a division between my people and thy people: to morrow shall this sign be.
Context
22 I will set apart in that day the land of Goshen, in which my people dwell, that no swarms of flies shall be there, to the end you may know that I am the LORD on the earth.
23 I will put a division between my people and your people. This sign shall happen by tomorrow.”’”
24 The LORD did so; and there came grievous swarms of flies into the house of Pharaoh, and into his servants’ houses. In all the land of Egypt the land was corrupted by reason of the swarms of flies.