Commentaries:
Barnes' Notes
Swarms of flies - Generally, supposed to be the dog-fly, which at certain seasons is described as a plague far worse than mosquitos. Others, however, adopt the opinion that the insects were a species of beetle, which was reverenced by the Egyptians as a symbol of life, of reproductive or creative power. The sun-god, as creator, bore the name Chepera, and is represented in the form, or with the head, of a beetle.
Other Barnes' Notes entries containing Exodus 8:21:
Psalms 78:45
Isaiah 7:18
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