Midrash su Numeri 28:27

6) (Vayikra 23:19) ("And you shall offer one kid of the goats as a sin-offering and two one-year old lambs as a sacrifice of peace-offerings.") "And you shall offer one kid of the goats as a sin-offering": I might think that the seven lambs and the kid of the goats mentioned in Bamidbar (Bamidbar 28:27, Bamidbar 28:29) are the same as those mentioned here. But when you come to bullocks and rams, you find that they are not so. (For here it is written "one year bullock and two rams," and there (Bamidbar 28:27) "two young bullocks" and "one ram.") But these are sacrificed because of the bread, and the others, because of the (festival) day.

(Bamidbar 28:27) "And you shall present a burnt-offering as a sweet savor to the L-rd": You sacrifice these aside from those mentioned in Torath Cohanim (Vayikra 27:18). "You say this; but perhaps they are the same as those mentioned there? — Can you say this? Are they similar? You cannot accept the second supposition, but the first — You sacrifice these aside from those mentioned in Torah Cohanim. "two young bullocks, one ram, etc.": If one found bullocks but not rams, or rams but not lambs, I might think that he does not sacrifice any until he finds all. It is, therefore, written "And you shall present a burnt-offering," implying even one. I might then think that even if all are found, (he may present only one). It is, therefore, written (to negate this) "two young bullocks, and one ram, etc."