Midrasch zu Dewarim 22:4

"help shall you help with him": What is the intent of this? From (Devarim 22:4) "Lift up shall you lift up with him" I might think that only loading (is commanded). Whence do I derive (the same for) unloading? From "help shall you help with him." R. Yoshiyah says: In both instances Scripture speaks of unloading. This tells me only of unloading. Whence do I derive (the same for) loading. It follows a fortiori, viz.: If unloading, which he (the owner of the animal) can do by himself, the other is commanded to assist him with, how much more so loading, which he cannot do by himself! Scripture speaks of the less obvious instance to derive therefrom the more obvious (by a fortiori reasoning) — whence R. Yishmael says: Just as unloading is (commanded) by the Torah, so, loading.

(Devarim 22:4) "You shall not see the ass of your brother or his ox fallen on the way and ignore them; lift up shall you lift up with him." "You shall not see the ass of your brother": This is a negative commandment. And elsewhere it is written (Shemoth 23:5) "If you see, etc.": That is a positive commandment. This tells me only of "the ass of your brother." Whence do I derive (the same for) the ass of your foe? From (Shemoth 23:5) "the ass of your foe." If so, why is it written (here) "your brother"? Scripture (there) speaks anent the evil inclination (i.e., Assist not only the ass of your brother, but even the ass of your foe — against the protestations of your evil inclination.)