[15] The Revised Version has “swarms of flies,” which is clearly an attempt to meet the case. But it is worth notice that in the Psalms the expression was twice rendered “divers kinds of flies” (lxxviii. 45, cv. 31, A.V.) The word occurs only of this plague.

Our Lord when on earth came not to destroy men’s lives. And yet it was necessary, for our highest instruction, that we should not think of Him as revealing a Divinity wholly devoid of sternness. Twice, therefore, a gleam of the fires of justice fell on the eyes which followed Him—through the destruction once of a barren tree, and once of a herd of swine, which property no Jew should have possessed. So now, when half the gloomy round of the plagues was being completed, it was necessary to prove that life itself was staked on this desperate hazard; and this was done first by the very same expedient—the destruction of life which was not human. There is something pathetic, if one thinks of it, in the extent to which domestic animals share our fortunes, and suffer through the brutality or the recklessness of their proprietors. If all men were humane, self-controlled, and (as a natural result) prosperous, what a weight would be uplifted from the lower levels also of created life, all of which groaneth and travaileth in pain together until now! The dumb animal world is partner with humanity, and shares its fate, as each animal is dependent on its individual owner.

The Expositor's Bible: The Book of Exodus — Part 99

We have already seen the whole life of Egypt stricken, but now the lower creatures are to perish, unless Pharaoh will repent. He is once more summoned in the name of “Jehovah, God of the Hebrews,” and warned that the hand of Jehovah, even a very grievous murrain (for so the verse appears to say), is “upon thy cattle which is in the field, upon the horses, upon the asses, upon the camels, upon the herds and upon the flocks.” Here some particulars need observation. Herds and flocks were everywhere; but horses were a comparatively late introduction into Egypt, where they were as yet chiefly employed for war. Asses, still so familiar to the traveller, were the usual beasts of burden, and were owned in great numbers by the rich, although rash controversialists have pretended that, as being unclean, they were not tolerated in the land.

The Expositor's Bible: The Book of Exodus — Part 99