Zevachim, Chapter 10, Mishnah 6. Until now, we have dealt with the laws of precedence regarding the offering of korbanos, and now the Mishnah moves on to discuss the laws of precedence regarding eating them: "Keshem shehen kodmin behakravatan, kach hen kodmin ba'achilatan" - just as they take precedence in being offered, so too they take precedence in being eaten.
The same two rules that establish the order of precedence for offering a korban - frequency and holiness - apply to the order of eating as well. A kohen who stands before chatas meat and shelamim meat and asks which he should eat first already has the answer: just as the chatas is offered first, it is also eaten first.
"Shelamim shel emesh veshelamim shel hayom" - shelamim of yesterday and shelamim of today:
It is worth noting the meaning of the word "emesh": in the language of the Chumash and in modern Hebrew, it means last night, but in Mishnaic Hebrew it means yesterday, similar to the Arabic word "ams". That is to say, we are dealing with shelamim that were offered yesterday as opposed to shelamim offered today. The allotted time for eating a shelamim is two days and the intervening night.
These two pieces of meat are equal in holiness, but their timeframes differ: the shelamim meat from yesterday will expire at sunset today and become nossar, whereas today's shelamim meat remains permitted to be eaten for over a day, until tomorrow. Therefore, the Mishnah rules: "Shel emesh kodmin" - the shelamim meat from yesterday is eaten first.
Two reasons were stated for this law:
Rashi's approach: It is disrespectful and disgraceful to leave the pieces of meat uneaten. Even though, naturally, a person would prefer fresh meat over yesterday's meat, it is improper to leave the meat until its allotted time expires. Therefore, yesterday's meat should be eaten today so that it does not become invalidated.
The Rambam's approach: The reasoning is primarily practical - the window of time for eating yesterday's meat is short, and once it passes, the owner of the korban will violate the prohibition of nossar. Therefore, the older pieces, which only have a few hours left, take precedence, whereas today's shelamim pieces still have more than twenty-four hours remaining.
A clash of rules: shelamim of yesterday versus a chatas or asham of today:
Here the Mishnah asks: What is the halachah when we have before us shelamim meat from yesterday as opposed to chatas or asham meat offered today? Two opposing considerations conflict with one another:
In terms of holiness: The rule "whatever is more holy than another takes precedence over it" applies, and the chatas and the asham - which are kodshei kodashim - are holier than the shelamim, which are kodashim kalim.
In terms of time: The allotted time for yesterday's shelamim ends at sunset, while today's chatas and asham meat may be eaten on a Biblical level all night long, and by Rabbinic decree until midnight. Consequently, there are six additional hours available to eat the chatas and the asham beyond the timeframe of the shelamim.
Which principle overrides the other?
Rabbi Meir: "Shelamim shel emesh kodmin" - the shelamim are eaten first, whether because of the practical reasoning that their window of time is narrow and there is a concern they might not be eaten, or because of the reason explained by Rashi, that it is improper to leave the meat until its time expires.
And the Chachamim disagree: "Chatas kodemes mipnei shehi kodshei kodashim" - the chatas and asham meat is eaten first because it is holier, in accordance with the rule "whatever is more holy than another takes precedence over it". And this is the halachah.
We see that wherever there is a rule of precedence based on holiness, it is the deciding factor, regardless of other practical considerations. The Sages rule that the chatas and asham precede, and even if the result is that the meat of the shelamim will be left over for a longer time, and even if ultimately it will not all be eaten - since a person's capacity to eat is limited - this is the halachah.
There is an important life lesson here: when principles and rules clash with pragmatic considerations - when things are inconvenient, or do not seem right, or things might go wrong on a practical level - the principles must stand firm. A person may not be practical when practicality means violating his principles. Rather, he must stick to his principles and let the chips fall where they may.
In summary: In this Mishnah, we learned that the rules of precedence that apply to offering sacrifices apply to eating them as well. Between two offerings of equal holiness, the one whose time limit is closer to expiring comes first - "shel emesh kodmin" - those of last night precede - whether due to the disrespect of leaving the meat over (Rashi) or out of concern for the prohibition of nosar (Rambam). However, in a clash between the consideration of time and the consideration of holiness - shelamim of last night versus a chatas and asham of today - Rabbi Meir and the Sages disagree, and the halachah follows the Sages: "chatas kodemes mipnei shehi kodshei kodashim" - a chatas precedes because it is a most holy offering, since the rule "kol hamekudash mechavero kodem es chavero" - whatever is more holy than another precedes the other - is the deciding factor even where practical considerations lean the other way.