Numbers 6:9

the head of his separation i.e. his head with the long hair, the symbol of his consecration.

in the day of his cleansing Better of his cleanness, i.e. in the day when he became clean.

shall he shave it The hair, being polluted, must be got rid of in some way that would prevent it defiling other objects. The present law does not mention this; but in accordance with ancient practice it would probably be buried (W. R. Smith, Rel. Sem.2 369 ff.); and this is laid down in the Mishnah.