Or HaChaim on Exodus 23:3/אור החיים על שמות כ״ג:ג׳

1 ודל לא תהדר בריבו, "And do not favour the poor in his litigation." The extra word בריבו contains a moral/ethical message based on Vayikra Rabbah 34, that the poor is liable to engage in a confrontation with G'd asking Him why He supplies everyone else with their needs whereas he is hungry and naked. Everyone who gives even a copper coin to a poor and thereby stills his hunger prevents the poor from complaining to G'd and accusing Him that G'd is not gracious to the poor. On the other hand, at times when no one on earth is gracious to the poor, his argument is very powerful. The Torah therefore commands us not to contribute to strengthening the voice of the poor who accuse G'd of insensitivity to their fate.