Albert Barnes Commentary Psalms 105:38

"Egypt was glad when they departed; For the fear of them had fallen upon them." — Psalms 105:38 (ASV)

Egypt was glad when they departed — They had suffered so many plagues; the land was so utterly desolate, and there was so much sorrow in their dwellings from the calamities which had come upon them for refusing to let the Israelites go, that at last they were glad to have them depart, and they were willing to aid them so that they might get rid of them. This, in part, accounts for the fact that they were willing to give them what they asked—even silver and gold—if they might thus facilitate their departure.

For the fear of them fell upon them — The fear of them, since they were under the protection of God; and the fear of the judgments which must follow if they continued to oppress them.