אִם־אַחֶ֖רֶת יִֽקַּֽח־ל֑וֹ שְׁאֵרָ֛הּ כְּסוּתָ֥הּ וְעֹנָתָ֖הּ לֹ֥א יִגְרָֽע׃
If he take him another wife, her food, her raiment, and her conjugal rights, shall he not diminish.
Rashi on Exodus
אם אחרת יקח לו IF HE TAKE HIM ANOTHER WIFE — besides her,
Sforno on Exodus
לא יגרע, one does not have the right to marry more than one woman unless able to provide for them not at the expense of reducing the first wife’s allowance. (Yevamot 65)
Rashbam on Exodus
שארה, her provisions (food) as in Micah 3,3ואשר אכלו שאר עמי, “the ones who devoured the flesh of my people.”