Exodus 10:21

Darkness which may be felt - Probably this was occasioned by a superabundance of aqueous vapors floating in the atmosphere, which were so thick as to prevent the rays of the sun from penetrating through them; an extraordinarily thick mist supernaturally, i.e., miraculously, brought on. An awful emblem of the darkened state of the Egyptians and their king.

Darkness - This infliction was specially calculated to affect the spirits of the Egyptians, whose chief object of worship was the Sun-god; and its suddenness and severity in connection with the act of Moses mark it as a preternatural withdrawal of light. Yet, it has an analogy in physical phenomena. After the vernal equinox the southwest wind from the desert blows some 50 days, not however, continuously but at intervals, lasting generally some two or three days. It fills the atmosphere with dense masses of fine sand, bringing on a darkness far deeper than that of our worst fogs in winter. The consternation of Pharaoh proves that, familiar as he may have been with the phenomenon, no previous occurrence had prepared him for its intensity and duration, and that he recognized it as a supernatural visitation.

10:21 We may observe concerning this plague. That it was a total darkness. We have reason to think, not only that the lights of heaven were clouded, but that all their fires and candles were put out by the damps or clammy vapours which were the cause of this darkness, for it is said, they saw not one another. That it was darkness which might be felt, felt in its causes by their finger - ends, so thick were the fogs, felt in its effects, (some think) by their eyes which were pricked with pain, and made the more sore by their rubbing them. Great pain is spoken of as the effect of that darkness, Rev 16:10, which alludes to this. No doubt it was very frightful and amazing. The tradition of the Jews is, that in this darkness they were terrified by the apparition of evil spirits, or rather by dreadful sounds and murmurs which they made; and this is the plague which some think is intended (for otherwise it is not mentioned at all there) Psa 78:49. He poured upon them the fierceness of his anger, by sending evil angels among them; for those to whom the devil has been a deceiver, he will at length be a terror to. It continued three days; six nights in one; so long they were imprisoned by those chains of darkness. No man rose from his place - They were all confined to their houses; and such a terror seized them, that few of them had the courage to go from the chair to the bed, or from the bed to the chair. Thus were they silent in darkness, 1Sam 2:9. Now Pharaoh had time to consider, if he would have improved it.