Exodus 8:18-22

18And the scribes did so with their sorceries, to bring forth gnats; but they could not. And the gnats were on man and on beast.

19Then the scribes said to Pharaoh, This is the finger of 1God! But Pharaoh's heart was stubborn, and he hearkened not to them, as Jehovah had said.

20And Jehovah said to Moses, Rise up early in the morning, and stand before Pharaoh — behold, he will go out to the water — and say to him, Thus saith Jehovah, Let my people go, that they may serve me.

21For, 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.

22And 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.