Exodus 12:38 - Wesley's Explanatory Notes

And a mixed multitude went up with them — Some perhaps willing to leave their country, because it was laid waste by the plagues. But probably the greatest part was but a rude unthinking mob, that followed they knew not why: It is likely, when they understood that the children of Israel were to continue forty years in the wilderness, they quitted them, and returned to Egypt again. And flocks and herds, even very much cattle — This is taken notice of, because it was long ere Pharaoh would give them leave to remove their effects, which were chiefly cattle.