Reference for Exodus 23:9

Our Rabbis were taught: He who annoys a stranger transgresses three negative commandments, and he who oppresses him transgresses two. Let us see, Regarding annoying, there are three negative commandments, (Ex. 22, 20; Lev. 19, 33 and 25, 17). If so, then there are three negative commandments concerning oppression also (namely, Ex. 22, 20; 23, 9 and 22, 24) — which include also the stranger. We must therefore say that in both cases, he transgresses three negative commandments.