If one vows to be a nazirite he must let the hair of his head grow and is forbidden to cut it; he is also forbidden to drink anything containing wine or to eat grapes or raisins or to become impure through contact with a corpse, as it says ["If a man or woman makes the vow of a nazirite... he shall abstain from wine or strong drink; he shall not drink vinegar of wine or of strong drink and shall not drink anything obtained by soaking grapes and shall not eat wet or dry grapes; all the days that he is a nazirite he shall not eat anything made from the grapevine, from grapestones to grapeskins; all the days of his nazirite vow] no razor shall touch his head... he shall let the head of his hair grow; [all the days that he is a nazirite to Ha-Shem he shall not come near a dead person... he shall not become impure...].^1,a

When the vow expires (if the Temple exists) the nazirite must bring three sacrifices and shave off his hair [as it says "On the day that his nazirite vow is fulfilled... the nazirite shall shave the hair of his head"]²; he is then no longer a nazirite. When the Temple does not exist all nazirites are perpetual.^b One cannot be a nazirite for less than 30 days. If one becomes a perpetual nazirite he can cut his hair once a year (and when the Temple exists, must bring the three sacrifices at each such time).^c If one's hair is cut he must add 30 days to the time of his vow; if one comes into certain types of contact with a corpse he must shave off his hair and start from the beginning (and when the Temple exists, must bring three sacrifices), as it says ["And if he becomes impure... he must shave his head on the day that he becomes pure... and keep the days of his nazirite vow...] and the first days fall away".^3,d

Sources:
1. Num. 6:2-7	a. 1:1; see 5:1-2
2. Num. 6:13-20	b. 2:20; 4:12; 8:lff
3. Num. 6:9-12	c. 3:1,12
	d. 6:1,3,11; 7:lff