The final mishnah of Nazir chapter 2 informs us that:
If one says, “I am hereby a nazirite when I will have a son,” and added, “I am hereby a nazirite from now for 100 days,” and then began observing the 100 days of his naziriteship, if a son is born to him up to 70 days from the start of his naziriteship, he has not lost anything.
If his son is born after 70 days, this negates the first 70 days, since shaving cannot be performed after a period of less than 30 days.
We’re dealing with a case of two terms of naziriteship that unexpectedly overlap. The 100-day period begins first, but since the 30-day birth naziriteship was declared first, it takes precedence. This means that when the baby is born, the 100-day naziriteship is paused while the new baby naziriteship takes effect. After the new baby naziriteship is observed, he completes his 100-day naziriteship.
If the baby is born in the first 70 days, the mishnah teaches, there is no problem — he can pause the original 100 day term of naziriteship, observe 30 days for his baby, and then go back and complete however many days are left on the 100-day naziriteship. However, because a nazirite must have at least 30 days’ worth of hair growth in order for the post-nazirite shave to be an act of significance, if less than 30 days of the first naziriteship remain when the child is born, instead of picking up where he left off, he has to start the 100-day term over from the beginning.
At least, this is one interpretation of the mishnah, and it winds up being fairly stringent: If there are less than 30 days left on your 100-day naziriteship when your baby is born, you have to start over. Other interpreters, however, suggest a less stringent ruling: You don’t have to start the 100-day naziriteship over again, but if less than 30 days remain you still have to observe a full 30 days to achieve requisite hair growth.
But it gets more complicated when we notice that the rule in our mishnah requiring 30 days’ worth of hair growth seems to be ignored by the previous mishnah, the penultimate mishnah of Nazir chapter 2:
If one said: “I am hereby a nazirite when I will have a son,” and “I am hereby a nazirite,” and he began counting his own term of naziriteship and during this period a son was born to him, he sets aside his own term of naziriteship and counts that which he vowed on condition of the birth of his son, and afterward he completes his own term of naziriteship.
The situation in this mishnah is just like our case except that both of the nazirite terms are 30 days (the default length of a naziriteship used in cases where no length of time is specified). But this mishnah suggests that after the personal term is suspended in favor of the one that is connected to the birth of a child, he doesn’t have to restart the full 30 days.
How then can he achieve the necessary hair growth? To resolve this dilemma, some commentators apply the rule from our mishnah to this case and say that when the person resumes the first term, he must serve as a nazirite for a full 30 days. But this doesn’t fit well with the language indicating that the person should pick up where he left off rather than start over.
Others suggest that in this case the person should delay shaving and bring both sets of offerings when the two terms of naziriteship are complete, thereby ensuring adequate hair growth. But of course, this leads to a new question: Why not apply this solution to the case in today’s mishnah as well?
While the Gemara is mostly silent about these questions, the conversation in the medieval commentaries is expansive. It’s one of those talmudic moments when it feels like every proposed solution gives rise to new questions and complexities multiply with each new layer of interpretation.
Read all of Nazir 15 on Sefaria.