מדרש על סוכה 111:20

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."