Moses announced this plague to Pharaoh like the first, in the morning near the Nile River ( Exodus 8:20; cf. Exodus 7:15). [source][source][source]
These insects were very annoying, even more bothersome than the gnats. [source][source][source]
"When enraged, they fasten themselves upon the human body, especially upon the edges of the eyelids. ... [1] not only tortured, "devoured" ( Psalm 78:45) the men, and disfigured them by the swellings produced by their sting, but also killed the plants in which they deposited their eggs ...." [2][source]
"The blood-sucking gadfly or dogfly was something to be abhorred and may in part have been responsible for the great deal of blind men in the land. ... It might also be noted that the Ichneuman fly, which deposits its eggs on other living things upon which its larvae can feed, was regarded as the manifestation of the god Uatchit." [3][source]
God demonstrated His sovereignty over space as well as nature and time by keeping the flies out of Goshen and off the Israelites ( Exodus 8:22). The exact location of Goshen is still unknown, but its general location seems to have been in the eastern half of the delta region of Egypt (cf. Genesis 46:28-29; Genesis 46:33-34; Genesis 47:1-6; Genesis 47:11). [4] Some of the commentators assumed that the first three plagues did not afflict the Israelites either, though the text does not say so explicitly (cf. Exodus 7:19; Exodus 8:2; Exodus 8:16-17). God distinguished between the two groups of people primarily to emphasize to Pharaoh that Israel"s God was the author of the plagues and that He was sovereign over the whole land of Egypt ( Exodus 8:23). [source][source][source]
For the first time Pharaoh gave permission for the Israelites to sacrifice to Yahweh ( Exodus 8:25), but he would not allow them to leave Egypt. Pharaoh admitted that Yahweh was specifically the God of Israel ("your God"), but he did not admit that he had an obligation to obey Him. [5][source]
The Egyptians regarded the animals the Israelites would have sacrificed as holy and as manifestations of their gods. Consequently the sacrifices would have been an abomination. [6][source]
". . . we know from excavations that this Pharaoh, Amenhotep II, worshipped bulls." [7][source]
The abomination that the Israelites" sacrifice would have constituted to the Egyptians also may have consisted in the method by which the Israelites would have sacrificed these animals. The Egyptians themselves practiced animal sacrifices, but they had rigorous procedures for cleansing their sacrificial animals before they killed them, which the Israelites would not have observed. [8][source]
Pharaoh agreed to let the Israelites leave Egypt to sacrifice temporarily in the wilderness after Moses reminded him of the problems involved in sacrificing in Egypt ( Exodus 8:28). Yet they were not to go very far from Goshen. Again Pharaoh asked Moses to pray that his God would remove the plague ( Exodus 8:28; cf. Exodus 8:9-10). [source][source][source]
"What is new in this fourth of the mighty Acts , apart from the nature of the miracle itself, is the separation of the land of Goshen from the effects of miracle (there has been no mention of Goshen"s fate in the earlier accounts), the negotiations between Pharaoh and Moses, with each of them setting conditions, and the allusion to the antipathy of the Egyptians to Israel worhsip [3]1 (or to Israelite ways, and to Israelites in general)." [10][source]