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.
Related Commentaries of Exodus 10:21
Exodus 10:21
21 And the LORD said unto Moses, Stretch out thine hand toward heaven, that there may be darkness over the land of Egypt, even darkness which may be felt.