חלק כחלק יאכלו, "portion for portion they shall eat it." According to the plain meaning of the text these words mean that the priests shall eat all that is given to them and share it out equitably among themselves, including the skins of the burnt-offerings, and the meat of the sacrifices which were not burned up totally.
לבד ממכריו על האבות, "except for transactions which had been arranged by the forefathers." If a priest has sold his house which he had inherited from his parents as described in Leviticus 25,33, the other priests cannot deny him his place in the משמר, roster, by saying that seeing he had sold his house and was relatively affluent he was not entitled to share the sacrificial meats with them. This is Ibn Ezra's interpretation of these words. As to the beginning of the paragraph commencing with the words: "when the Levite will come" (verse 6), this refers to a priest who is a member of the tribe of Levi. The verse does not speak at all about a Levite who is "only" a Levite, seeing the words: "who stands and performs service" could not apply to a mere Levite. When verse 6 continues ובא בכל אות נפש, "and he may come whenever he likes to the place, etc.," this teaches that a priest may offer his personal sacrifices even out of turn, during the roster of other priests. Similarly, during the pilgrimage festivals Pesach, Shavuot, and Sukkot, every priest is entitled to participate in the sacrificial service and offer the respective offerings of his own on the festival. (Sifri Shoftim 168)
A Midrashic approach: the words חלק כחלק יאכלון mean that the priests share equally, as we pointed out already. This might lead me to believe that on the festivals all the priests are entitled to share equally also in such sacrifices as the daily public offerings, offerings which have nothing to do with the festivals. To tell us that this is not so the Torah added the words לבד ממכריו על האבות, i.e. except for the matters which were sold already in the days of the forefathers, i.e. at the time when King David organised the division of the משמרות, the "rosters," i.e. that the priests have to take turns, each one belonging to one of 24 groups each of which had 2 weeks of service in the Temple allocated to it. At that time the priests were considered as "having sold" the rights to certain weeks of service to each of these various groups, rosters. (compare Sukkah 55-56). They would say to each other: "you serve during my week and I will serve during your week." The "sale" was not one in which money changed hands.
We have to ask ourselves that seeing originally every priest was allowed to perform sacrificial service whenever he wanted to, what prompted King David and Samuel to change a system which had been functioning for 400 years? Why did they institute these rosters which limited the periods of service by each priest to 2 weeks a year of which each priest actually served only on a single day of 'his week?' Besides, what was the reason for dividing these rosters into 24? According to the Talmud this division was so absolute that a priest could under no circumstances switch, or exchange his membership in one roster to becoming a member of a different roster. We know of the absolute rigidity of this order from Sukkah 56 where the exact division of who was entitled to what is discussed if the festival occurred in the middle of the week, depriving at least one roster of part of its exclusive claim to that week.
The place in the courtyard of the Temple where the members of the roster divided their shares was allocated in such a way that all the onlookers could know which roster was the incoming one and which was the outgoing one. The members of each roster were known by names identifying their roster so as to enable easy identification. The Talmud relates that it happened that a member of a roster called Bilgah disgraced itself and that henceforth the authorities punished the entire roster by allocating a place to it during the entire week it was performing its service which made it appear as if this roster was about to finish its service on that day. It appears that the hands of the authorities were severely limited in the kind of punishment they could administer for laxity or deliberate misconduct by its members as these 24 rosters were perceived as paralleling similar rosters among the angels performing the service in the celestial counterpart of the Sanctuary on earth. According to the Sefer Habahir (item 107) there were 3 times 24 such rosters in the celestial regions corresponding to the three verse in Exodus 14, 19-21 each one of which has 72 letters, each if read vertically representing one of the 72-lettered name of God. It appears that whereas the "rosters" i.e. procedures in the celestial regions were fixed, God created new angels every day who would sing His praises prior to disappearing. The forefathers, i.e. David and Samuel
(Taanit 27), in their wisdom decided to pattern service in the terrestrial Sanctuary to reflect as much as possible what they knew about what went on in the celestial spheres. The blessing pronounced by the members of the outgoing roster for the incoming roster included the following passage: "may the One who resides in this House ensure that there is peace and mutual goodwill among you just as peace and goodwill prevails in the celestial regions where there is no jealousy or hatred between the angels, but they all co-exist in peace and comradeship"
(Berachot 12). At any rate, we have seen that a great deal of thought was invested by the leaders of earlier generations in arriving at the arrangement of who does what and when in connection with the Temple service.