NET

21 If you do not release my people, then I am going to send swarms of flies on you and on your servants and on your people and in your houses. The houses of the Egyptians will be full of flies, and even the ground they stand on.

Darby

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.

KJV

21 Else, if thou wilt not let my people go, behold, I will send swarms [of flies] upon thee, and upon thy servants, and upon thy people, and into thy houses: and the houses of the Egyptians shall be full of swarms [of flies], and also the ground whereon they [are].