The Sharia of Moses in the TORA
Part 1 - The 248 Positive Commandments of the Tora
203 - ASSISTING THE OWNER IN LIFTING UP HIS BURDEN
Maimonides makes the assistance prescribed in this commandment obligatory whether the burden is to be loaded on the beast or on its owner.
The obligation to assist in unloading precedes that of loading, since relief is also afforded to the beast in removing its burden. If an occasion should occur for performing the obligation both for a friend and for an enemy, both requiring help at the same time, the enemy takes precedence over the friend even where the latter is unloading, and the former is only loading. The reason for this provision is that a man should learn to conquer his selfish instincts.*