Notes on the Bible, by Albert Barnes, , at sacred-texts.com
The locusts - The locust is less common in Egypt than in many eastern countries, yet it is well known, and dreaded as the most terrible of scourges. They come generally from the western deserts, but sometimes from the east and the southeast. No less than nine names are given to the locust in the Bible, of which the word used here is the most common (ארבה 'arbeh); it signifies "multitudinous," and whenever it occurs reference is made to its terrible devastations.
The face - Literally, cover "the eye of the earth," alluding to the darkness which follows, when the whole atmosphere is filled on all sides and to a great height by an innumerable quantity of these insects.
Shall eat every tree - Not only the leaves, but the branches and even the wood were attacked and devoured. The Egyptians were passionately fond of trees.
Fill thy houses - The terraces, courts, and even the inner apartments are said to be filled in a moment by a locust storm. Compare Joe 2:9.
For the first time the officers of Pharaoh intervene before the scourge is inflicted, showing at once their belief in the threat, and their special terror of the infliction. Also, for the first time, Pharaoh takes measures to prevent the evil; he does not indeed send for Moses and Aaron, but he permits them to be brought into his presence.
Let the men go - i. e. the men only, not all the people. See Exo 10:8.
With our young ... - The demand was not contrary to Egyptian usage, as great festivals were kept by the whole population.
Evil is before you - i. e. "your intentions are evil." Great as the possible infliction might be, Pharaoh held it to be a less evil than the loss of so large a population.
An east wind - See Exo 10:4. Moses is careful to record the natural and usual cause of the evil, portentous as it was both in extent and in connection with its denouncement.
Went up - At a distance the locusts appear hanging, as it were, like a heavy cloud over the land; as they approach they seem to rise, and they fill the atmosphere overhead upon their arrival.
Over all the land - Travelers mention a cloud of locusts extending over 500 miles, and so compact while on the wing that it completely hid the sun. This passage describes a swarm unprecedented in extent.
This death only - Pliny calls locusts a pestilence brought on by divine wrath. Pharaoh now recognizes the justice of his servants' apprehensions, Exo 10:7.
West wind - Literally, "a sea wind," a wind blowing from the sea on the northwest of Egypt.
Red sea - The Hebrew has the "Sea of Suph": the exact meaning of which is disputed. Gesenius renders it "rush" or "seaweed;" but it is probably an Egyptian word. A sea-weed resembling wood is thrown up abundantly on the shores of the Red Sea. The origin of the name "Red" Sea is uncertain: (naturalists have connected it with the presence of red infusoria, Exo 7:17).
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.
Had light in their dwellings - The sandstorm, if such were the cause, may not have extended to the district of Goshen; but the expression clearly denotes a miraculous intervention, whether accomplished or not by natural agencies.
Your flocks and your herds - Pharaoh still exacts what would of course be a complete security for their return: but the demand was wholly incompatible with the object assigned for the journey into the wilderness.