מדרש על במדבר 6:14

(Bamidbar 6:14) "And he shall offer up his sacrifice to the L-rd: one lamb of the first year, whole": to exclude one that is blemished. "and one ewe-lamb of the first year, whole": to exclude one that is blemished. "and one ram, whole": to exclude one that is blemished. We are hereby taught that the Nazirite requires three (mutually exclusive) animals (i.e., each is a mitzvah in itself).