John Calvin 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)

And a mixed multitude. Although Abraham possessed many servants, it is hardly probable that during the famine Jacob maintained any persons in his family other than his own children, whom he could barely sustain enough to keep them from dying of hunger. And since Moses, in relating their coming into Egypt, does not mention any servants, we may conjecture that they brought no great number, because necessity compelled them to be content with a few. From this we gather that the mixed multitude, which joined the Israelites, were either the offspring of Egypt or had migrated from the neighboring countries to settle there, as fertile lands often attract many strangers with the pleasures of abundance.

The same expression is used in Nehemiah 13:3, where it is said that the mixed multitude was separated from the true Israelites, lest all should indiscriminately arrogate to themselves the same dignity, and thus the Church should be polluted by a confused mixture. But if anyone should think it absurd that ungodly men, with no better hope before them, would voluntarily forsake a rich and convenient dwelling to seek a new home as wanderers and pilgrims, let him remember that Egypt had by then been afflicted by so many calamities that its very poverty and devastation might easily have driven away its inhabitants. A great part of the cattle had perished; all the fruits of the earth were ruined; the fields were ravaged and almost desert. We need not, therefore, wonder if despair caused many sojourners to flee, and even some of the natives themselves. It is also possible that, having been inhumanly treated, they shook off the yoke of tyranny when a way to liberty was opened to them.

But although God gave His people a ready departure, He still did not choose to let them go out altogether without any inconvenience. For they did not go out satisfied with food, nor having dined delicately, but were compelled to carry unbaked dough in their bags, to eat bread hastily baked on embers during their journey. By this example we are taught that God’s blessings are always mingled with certain inconveniences, lest too much delight should corrupt the minds of the godly.