Commentary for Exodus 23:5

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).

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.]

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.