Exodus 8:21

But if you will not let My people go, I will send swarms of flies upon you and your officials and your people and your houses. The houses of the Egyptians and even the ground where they stand will be full of flies.

Note Literally a noxious mixture; also in verses 22, 24, 29, and 31

BSB · Berean Standard Bible
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.

Note swarms…: or, a mixture of noisome beasts, etc

KJV · King James Version
Else, if you will not let my people go, behold, I will send swarms of flies on you, and on your servants, and on your people, and into your houses. The houses of the Egyptians shall be full of swarms of flies, and also the ground they are on.
WEB · World English Bible
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.
ASV · American Standard Version

Related passages

From the Treasury of Scripture Knowledge, grouped by the word they explain.

swarms
or, a mixture of noisome beasts, etc. The word {arov} is rendered [kunomwea,] kunomuia,] the dog-fly, by the LXX. (who are followed by the learned Bochart,) which must have been particularly hateful to the Egyptians, because they held dogs in the highest veneration, under which form they worshipped Anubis.
Psalm 78:45; Psalm 105:31; Isaiah 7:18