Charles Ellicott Commentary Exodus 12:38

"And a mixed multitude went up also with them; and flocks, and herds, even very much cattle." — Exodus 12:38 (ASV)

A mixed multitude went up also with them. — Nothing is told to us of the component elements of this “mixed multitude.” We hear of them as “murmuring” in Numbers 11:4, so that they seem to have remained with Israel.

Some may have been Egyptians, impressed by the recent miracles; some foreigners held in servitude, like the Israelites, and glad to escape from their masters. It is noticeable that the Egyptian writers, in their perverted accounts of the Exodus, made a multitude of foreigners (Hyksôs) take part with the Hebrews.