Numbers 6:20

And the priest shall take the sodden shoulder of the ram, and one unleavened cake out of the basket, and one unleavened wafer, and shall put them upon the hands of the Nazarite, after the hair of his separation is shaven:

This is the law of the Nazarite who hath vowed, and of his offering unto the LORD for his separation, beside that that his hand shall get: according to the vow which he vowed, so he must do after the law of his separation.