Parashat Tzav begins with the command to clean the altar of its ashes each morning, and the Torah introduces this command by stating that the sacrifices would burn on the altar throughout the night, thus producing ashes which needed to be cleared (6:2). Rashi comments that this verse teaches that hekter chalavim ve-eimurin – the placing of the sacrificial animal parts which are to be burnt on the altar – may be done throughout the night. Although generally the rituals in the Beit Ha-mikdash may not be performed at night, hekter chalavim ve-eimurin marks an exception, and it may be done even during the nighttime hours.
This halakha is discussed, interestingly enough, in the very first Mishna in the Talmud – the opening Mishna of Masekhet Berakhot. The Mishna there cites Rabban Gamliel as telling his sons that although the Torah obligation to recite the nighttime shema may be fulfilled throughout the night, the Sages enacted a provision requiring that it be recited before chatzot (halakhic midnight). This was done as a safeguard to ensure that people would not go to sleep at night before performing this vitally important mitzva. Rabban Gamliel then added that regarding other nighttime mitzvot, too, Chazal enacted a safeguard requiring performing them by chatzot. Specifically, he mentions hekter chalavim ve-eimurin, and the consumption of sacrificial meat. Certain sacrifices may be eaten throughout the night after the offering is brought (as opposed to other sacrifices, which may also be eaten the next day), but the Sages enacted a provision requiring eating sacrificial meat before chatzot.
Rashi, in his commentary to the Mishna, offers a very surprising – and strained – reading of Rabban Gamliel’s remark, distinguishing between hekter chalavim ve-eimurin and the consumption of the sacrificial meat. Although Rabban Gamliel mentioned both, Rashi claims that he referred only to the consumption of sacrifices, not to the placing of sacrifices on the altar. When it comes to the latter, the Sages did not enact any safeguard, and the kohanim were permitted to place the required portions of the sacrifices on the altar throughout the night, even though they required consuming the meat before chatzot. This is in contrast to the simple reading of the Mishna, and indeed, other Rishonim disagreed with Rashi’s view. The Rambam, in his commentary to this Mishna, as well as in Hilkhot Ma’aseh Ha-korbanot (4:2) and Hilkhot Temidin U-musafin (1:6), writes that hekter chalavim ve-eimurin was allowed only until chatzot. This is also the view taken by Tosafot (Pesachim 120b). The different views on this subject are noted by Meiri, in his commentary to Masekhet Berakhot.
In explaining Rashi’s surprising position, the Tzelach notes Rashi’s formulation in describing this halakha: “They forbade them [the sacrifices] for consumption even before their [final] time so that one will not end up eating them after daybreak and thus be liable to kareit…” Rashi here emphasizes that eating sacrificial meat past the deadline established by the Torah constitutes an especially grave violation, punishable by kareit (eternal spiritual excision). He then proceeds to explain that a similar enactment was made regarding the nighttime shema recitation because people would otherwise be prone to delaying the recitation and thus forfeit the mitzva. The Tzelach infers from Rashi’s comments that the Sages were not inclined to legislate this safeguard for all nocturnal obligations, but only for those which are more likely to be neglected (shema), or when an especially grave prohibition is at stake (eating sacrifices). Placing sacrifices on the altar past the allotted time is forbidden, but this violation is not punishable by kareit, and this is not an offense that kohanim are prone to commit.
The Tzelach draws further support from Rashi’s comments in Masekhet Yevamot (119a) in reference to the Gemara’s comment that in situations of safeik (“doubt”), where there is a risk of a Torah violation, no distinctions are made between different levels of violations. Whenever we are dealing with a potential transgression of a Torah prohibition, we must act stringently to avoid possible violations, irrespective of their level of gravity. (The Gemara’s formulation is, “Ma li issur kareit, ma li issur lav.”) Rashi, commenting on the Gemara’s discussion, finds it necessary to clarify that the Gemara’s comment applies only to situations of “safeik,” and not to “harchaka” – enacting additional restrictions to safeguard the Torah’s laws. When determining when to enact safeguards, Rashi writes, Chazal certainly took the gravity of every prohibition into account. Indeed, we find many more provisions safeguarding against capital offenses (such as Shabbat, for example) than we do safeguarding other Torah prohibitions. Understandably, then, Rashi in Masekhet Berakhot distinguished between the placement of sacrifices on the altar and the consumption of its meat. Since consuming sacrificial meat past chatzot constitutes an especially grave violation, Chazal moved the deadline from daybreak to chatzot to protect against violations, but they enacted no such provision regarding the placement of the sacrifice on the altar.