וְגַם־עֵ֥רֶב רַ֖ב עָלָ֣ה אִתָּ֑ם וְצֹ֣אן וּבָקָ֔ר מִקְנֶ֖ה כָּבֵ֥ד מְאֹֽד׃
И смешанное множество поднялось и с ними; и стада, и стада, даже очень много скота.
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.”