Whence is it derived that all of the watches share equally in the devoted portions of the offerings and in the portion of the show-bread? From (Ibid. 8) "Portion as portion shall they eat, viz.: Just as they share in the sacrificial service, so they share in the eating (of the show-bread).
I might think that the same held true for (obligatory) offerings brought on the festival not for the sake of the festival (i.e., that with these, too, all watches served and shared alike); it is, therefore, written (Ibid.) "aside from the sale of the fathers" — what the fathers sold to each other, i.e., "I on my Sabbath and you on your Sabbath."