כִּֽי־תִרְאֶ֞ה חֲמ֣וֹר שֹׂנַאֲךָ֗ רֹבֵץ֙ תַּ֣חַת מַשָּׂא֔וֹ וְחָדַלְתָּ֖ מֵעֲזֹ֣ב ל֑וֹ עָזֹ֥ב תַּעֲזֹ֖ב עִמּֽוֹ׃ (ס)
Siehst du den Esel deines Hassers zusammenbrechen unter seiner Last, und du wolltest unterlassen, es ihm leichter zu machen — mache es ihm leichter.
Rashi on Exodus
כי תראה חמור שנאך וגו׳ IF THOU SEE THE ASS OF HIM THAT HATETH THEE etc. — כי here has the meaning of “possibly”, “perhaps”, which is one of the four meanings which the word כי serves to express. The sense of the verse is accordingly the following: Can you possibly see his ass crouching beneath his burden and forbear to help him? (The Hebrew word בתמיה in Rashi means “Say this in the intonation of a question”, and is nothing more than our question mark).
Rashbam on Exodus
חמור שנאך, the Torah uses the most likely scenario as its model. [Clearly, you are to do no less for the animal of a friend or relative.]
Tur HaArokh
וחדלת מעזוב לו, “and you would refrain from assisting him;” this is a veiled warning that you must not dare abandoning him to his problems just because the owner of the beast has a record of being hostile to you. On the contrary, you must make every effort to assist such a person, provided he too does his share in enabling the overloaded beast to get rid of its burden.