Rashi on Exodus
ערב רב A MIXED MULTITUDE — a mingling of various nations who had become proselytes.
Sforno on Exodus
וצאן ובקר, of the mixed multitude who were leaving Egypt with the Israelites to take up residence among them together with all their belongings.
Rashbam on Exodus
ערב רב, an expression describing a mixed assortment, as we find it in Psalms 106,35 ויתערבו בגוים, “they mixed freely with the gentiles, assimilated.”