Rashi on Exodus 23:9/רש"י על שמות כ״ג:ט׳

1וגר לא תלחץ AND THOU SHALT NOT OPPRESS THE STRANGER — In numerous passages (36 in number) does the Torah offer a caution about the ill-treatment of the stranger, because his original character is bad (Bava Metzia 59b).

2אח נפש הגר [FOR YE KNOW] THE SOUL OF A STRANGER — how hard it is for him when people oppress him.