In the very last Halacha of Hilchot Maaseh Hakorbanot, Maimonides writes:

Gentiles are permitted to offer burnt offerings to G‑d in all places, provided they sacrifice them on a raised structure that they build. It is forbidden to help them [offer these sacrifices] or act as agents for them, for we are forbidden to sacrifice outside [the Temple Courtyard]. It is permitted to instruct them and teach them how to sacrifice to the Almighty, blessed be He.1

Maimonides’ source for this law is the Talmud in Tractate Zevachim.2 But the Talmud adds an addendum:

This is similar to that incident in which Ifera Hurmiz, the mother of King Shapur of Persia, sent an offering to Rava, with which she sent this message to him: Sacrifice this for me, for the sake of Heaven. Rava said to Rav Safra and to Rav Acḥa bar Huna: Go, take two gentile youths of the same age, i.e., similar to one another, so that the sacrifice will be performed with maximal beauty, and see where the sea currently raises silt, which is a place that no one has used before. And take new wood and bring out fire from new vessels, and the two youths will sacrifice the offering for her, for the sake of Heaven.3

It is clear that there are additional details regarding exactly how a non-Jew is to offer a sacrifice that are pertinent here. Namely:

1. The sacrifice must be carried out in an aesthetically pleasing manner.

2. The ground used for the altar must not have been used for any other purpose prior to this.

3. The wood used must be specifically hewn for this purpose, i.e, recycled wood must not be used.

4. Lastly, the flint stone used must be entirely new.

The obvious question for Maimonides is: why not include these details? If one is permitted to instruct a non-Jew how to offer a sacrifice, it only makes sense to provide all the relevant information.

The Lubavitcher Rebbe raises this issue and provides a possible solution.4 He suggests that Maimonides omits the details because he believes they are not integral to the sacrifice. There is an extremely strict protocol which must be followed for Temple sacrifices. If one detail is off—even something as seemingly minute as the intent of the Kohen—the entire sacrifice is void. For a non-Jew acting on his own, however, there is no such protocol.

True, as is evident from the Talmud above, effort must be taken to ensure that the sacrifice is carried out in a respectful and aesthetically pleasing manner. Exactly what form that takes, however, is not defined. This is why Maimonides does not quote the anecdote from the Talmud: the description of that particular sacrifice is not a blueprint for how such sacrifices must always be carried out.

This idea—that when a non-Jew offers a sacrifice outside of the Temple the rules are less defined— is illustrated by one detail in the infamous lead up to the destruction of the Second Temple.

Non-Jews may offer burnt offerings in the Holy Temple, but all the rules pertaining to sacrifices apply. In the infamous episode of Kamtza and Bar Kamtza, after Bar Kamtza was scorned at the feast, he resolved to take revenge on the entire community (since the attending rabbis did nothing to allay his humiliation.) He approached the emperor and declared, “The Jews are rebelling against you!”

To see if this was indeed the case, the emperor sent an offering with Bar Kamtza to be brought to the Temple. Along the way, Bar Kamtza made a small blemish which would invalidate the sacrifice. The Talmud comments that this would not be considered a blemish if a non-Jew were offering a sacrifice outside the Temple. There, the animal would only be invalid if it was missing a limb.5 So we see that the rules for a non-Jew to offer a sacrifice outside the Temple are not quite as stringent.

Practical Application

Contained in Hilchot Maaseh Hakorbanot are the myriad laws relating to the sacrifices we are obligated to offer in the Temple. However, Maimonides saw fit to dedicate the conclusion of these laws to the sacrifices of non-Jews. This illustrated the importance of positively influencing those around us. The Jewish Nation is to be a “Light unto the Nations.”6 We are charged with providing a moral compass to society as a whole.

This, explains the Rebbe, is the kernel embedded in the last law of Hilchot Maaseh Hakorbanot. Instructing a non-Jew how to offer a sacrifice means illustrating to all nations how G‑d demands that we all set ourselves—our desires and mundane pursuits—aside for the sake of G‑d. The Jewish Nation must impart a vision of universal morality as embodied in the Seven Noahide Laws.