Exodus 8:21-23

Darby Translation

²¹ For, if thou do not let my people go, behold, I will send dog-flies upon thee, and upon thy bondmen, and upon thy people, and into thy houses; and the houses of the Egyptians shall be full of dog-flies, and also the ground on which they are.

²² And I will distinguish in that day the land of Goshen, in which my people dwell, that no dog-flies shall be there; that thou mayest know that I Jehovah am in the midst of the land.

²³ And I will put a separation between my people and thy people; to-morrow shall this sign be.