2,879. From One Nezirus Period to Another

Hilchos Nezirus 4:2

If a person makes two nazirite vows, he shaves for the first on the thirty-first day and for the second on the sixty-first day. If he shaved for the first on the thirtieth day, then he shaves for the second on the sixtieth day. If he shaved for the second on the fifty-ninth day, he has fulfilled his obligation because the thirtieth day also counts towards his second nezirus period.

Hilchos Nezirus 4:3

Let’s say that someone declares himself to be a nazir, plus he says that he will be a nazir if a son is born to him. If he starts observing nezirus and then a son is born to him, he completes his own nezirus and then starts observing the nezirus for his son. Now let’s say that he says that he will be a nazir if a son is born to him, plus that’s he’s a nazir for certain days. If he starts observing his own nezirus and then a son is born to him, he interrupts this nezirus and starts observing the nezirus for his son, after which he goes back and completes his original nezirus; these are both considered like a single nezirus period. Accordingly, if he is rendered unclean during the nezirus for his son, everything is cancelled out; if he is rendered unclean after the nezirus for his son, when he has resumed observing his own nezirus, then only until the nezirus for his son is cancelled out. How many days must he observe to complete his own nezirus? If 30 or more days of his nezirus remained after his son was born, he observes the nezirus for his son and then completes the rest of the days for his own nezirus. If fewer than 30 days remain from his nezirus, then he must observe 30 days after the nezirus for his son. This is because there are never fewer than 30 days between shaving for two nezirus periods.