Nazir 3:3-4

Nazir 3:3

If one says, “I am a nazir” and he is rendered ritually impure on day 30, he loses all the days he has observed. Rabbi Eliezer says that he only loses seven days in this case but if one said, “I am a nazir for 30 days” and he becomes ritually impure on day 30, then he loses all the days.

Nazir 3:4

If one says, “I am a nazir for 100 days” and he becomes ritually impure on day 100, he loses all the days. Rabbi Eliezer says that he only loses 30 days. If he is rendered ritually impure on day 101 (finishing his 100 days but before he shaves and brings his sacrifices), he loses 30 days; Rabbi Eliezer says seven days.