Sforno on Leviticus 19:33/ספורנו על ויקרא י״ט:ל״ג

1After the Torah warned that the Torah scholars, etc., must be shown due respect, it also warns us not to treat with disdain people who are on the lower rung of the economic ladder. וכי יגור אתך גר לא תונו אותו, even if this unfair treatment consists only of words, not deeds. The Torah continues,