מדרש על במדבר 7:87

(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.