מדרש אויף במדבר 7:87

“All the cattle for the burnt offering: twelve bulls, twelve rams, twelve lambs in their first year, and their meal offering, and twelve goats as a sin offering” (Numbers 7:87).
“All the cattle for the burnt offering: twelve bulls” – why is it stated? It is because it says: “One young bull” (Numbers 7:15), and I do not know whether it is fit to be a burnt offering or not, because “as a burnt offering” (Numbers 7:15) is stated only regarding the lamb. From where is it derived that all of them were fit to be a burnt offering? That is why it said: “All the cattle for the burnt offering”; it is to tell you that all of them were fit to be a burnt offering. They ascribe to each and every one of them as though he sacrificed twelve bulls. These were the ones that they donated, and no disqualification befell any of them.
“Twelve rams, twelve lambs” – the verse inserted the rams between the bulls and the lambs to say: Just as the bulls and the lambs that were designated as burnt offering are all fit to be burnt offerings, so too, the rams were all fit to be burnt offerings. They ascribe to each and every one of them as though he sacrificed twelve rams and twelve lambs. These were the ones that they donated, and no disqualification befell any of them.

(Bamidbar 7:15) "One young bullock": There was no other like it in its herd. "one ram": There was no other like it in its herd. "one lamb of its first year": (within) its first year, and not the (one-year) count of the world. "one lamb … for a burnt-offering": We are hereby taught that all are valid as a burnt-offering. — But perhaps "a lamb," where it is explicitly stated, is valid, but the others not! It is, therefore, written (Ibid. 87) "All the cattle for the burnt-offering: twelve bullocks, etc.", to indicate that all are valid as burnt-offerings.

(Bamidbar 7:87) "All the cattle for the burnt-offering: twelve bullocks, etc." Why is this mentioned? It is written (Ibid. 15) "One young bullock, one ram, one lamb of its first year for a burnt-offering." We are hereby taught that they are all valid as a burnt-offering. — But perhaps only the lamb, where it is explicitly written, is valid as a burnt-offering, but not the others. It is, therefore, written "All the cattle for the burnt-offering." We are here apprised that they are all valid as a burnt-offering. And it is accounted to each one as if he had offered twelve young bullocks, twelve rams, twelve lambs, and twelve he-goats. And they were the same that were donated, no unfitness having befallen them.