The 203rd mitzvah is that we are commanded to [help a person] load a burden on an animal or on himself1 if he is alone, once it has been unloaded by us or by someone else. Just as we are commanded to remove a load,2 so too we are commanded to help him reload.

The source of this commandment is G‑d's statement3 (exalted be He), "You must help him pick up [the load]."

In the words of the Mechilta: "The phrase 'you must help him pick up [the load]' refers to loading."

The details of this mitzvah are explained in the second chapter of tractate Bava Metzia.4 There it is explained that there is one Biblical commandment to unload and another Biblical command­ment to load.