פּירוש אויף שמות 2:17

ויגרשם AND THEY DROVE THEM AWAY, because of the banishment into which their father and his family had been driven (Midrash Tanchuma, Shemot 11).

ויקם משה ויושיען, “Moses arose and saved them.” From the use of the word: “he arose,” it is clear that that the male shepherds had thrown Yitro’s daughters into the troughs, as a punishment for their father who had become an outcast for his religious beliefs, and who had rejected idolatry as a result. (Sh’mot Rabbah 1,32.) The expression ויושע makes it clear that the persons helped had been in mortal danger as we know from Psalms 69,2: הושיעני אלוקים כי באו מים עד נפש, “deliver me, O G–d, for the waters have reached my (soul) neck.”

ויקם משה ויושיען, seeing that both parties to this argument were non-Jewish, Moses did not intervene by avenging the wronged party but only made sure that he would redress the injustice done to the innocent party.