C. F. Keil and Franz Delitzsch on Exodus 8:16-17

Exo 8:16-17

The Gnats, or the third plague. - The כּנּם, or כּנּים (also כּנּם, probably an old singular form, Ewald, §163 f), were not “lice,” but σκνῖφες, sciniphes, a species of gnats, so small as to be hardly visible to the eye, but with a sting which, according to Philo and Origen, causes a most painful irritation of the skin. They even creep into the eyes and nose, and after the harvest they rise in great swarms from the inundated rice-fields. This plague was caused by the fact that Aaron smote the dust of the ground with his staff, and all the dust throughout the land of Egypt turned into gnats, which were upon man and beast (Exo 8:17). “Just as the fertilizing water of Egypt had twice become a plague, so through the power of Jehovah the soil so richly blessed became a plague to the king and his people.”