תלמוד על שמות 23:9

R. Eliezer b. Jacob said: Because [the proselyte’s] original nature was evil,⁵[When he was a heathen, and ill-treatment by an Israelite may have the effect of making him relapse.] Scripture gave many warnings in connection with him, as it is stated, And a stranger shalt thou not wrong, neither shalt thou oppress him; for ye know the heart of a stranger.⁶Ex. 23, 9. Hence because his original nature was evil, Scripture gave many warnings concerning him.