As we learned on yesterday’s daf (=page) the second perek (=chapter) of Masechet Zevahim deals with situations where there is some problem with the person who brings the sacrifice. One of the examples that appears in the Mishnah is the case of an onen who sacrifices. An onen is someone who has a close relative who has passed away, but has not yet been buried. Generally speaking, Jewish law anticipates that such a person is supposed to focus entirely on tending to the deceased and is free of all other mitzvot.
A number of reasons are suggested by the Gemara as possible sources for the law forbidding an onen from carrying out the sacrificial service.
The first suggestion is that we learn it from the passage about a kohen gadol – a High Priest – who is commanded to continue his service in the Temple even after a close relative has died (see Vayikra 21:12). According to that pasuk(=verse), which says lo yetze ve’lo yehalel, the kohen gadol cannot leave the Temple, and that in doing so his service will not become mehulal – made mundane. The implication, as understood by the Gemara, is that this is a unique law pertaining to the kohen gadol, but if any ordinary kohen in that situation were to remain in the Temple, his service would become mehulal.
Both Rashi and the Rambam in his Sefer HaMitzvot (principle number 5) understand from the Gemara that the term ve’lo yehalel is not a prohibition for the High Priest to make his service mundane by leaving the Temple, rather it is an explanation of why he is required to remain at his post – his service will not be affected by his status as an onen, even though the status of other kohanim would be affected. The Ramban disagrees with this approach, noting that many of theGe’onim do seem to count ve’lo yehalel as a prohibition forbidding the High Priest from leaving the Temple when he is anonen. He suggests that the Gemara should be understood as saying that there is a unique law forbidding the kohen gadolfrom leaving the Temple when he is an onen, since were he to leave, it would render his service mundane. The service of ordinary priests, however, would not be mehulal were they to leave the Temple – since were their service acceptable theTorah would not permit them to leave.