If one said: I am hereby a nazirite when so-and-so will have a son, and another heard and said: And I - this inquiry is likewise relevant if he said "ועלי – and it is incumbent upon me". [Rather, the gemara chose one of the formulas.] So from the Teacher.

What is the halakha - do we say since he responded to the other man away from the presence of the father of the [baby] son, the matter would not be embarrassing for him? And that he spoke about himself, that "I will be a nazirite when I have a son".

Or perhaps this is what he is saying to him: I love so-and-so as you do - when he will have a son, I will be a nazirite as you are. The dilemma remains unresolved.

Mishna. In a case where one said: I am hereby a nazirite now, and I will be a nazirite when I will have a son. He began counting his own term of naziriteship, and before completing his own [first] term, his son was born, and his naziriteship which he vowed to take upon having a son took effect upon him.

He first completes his own initial term of naziriteship - because he accepted it upon himself first, and afterwards he counts the term of naziriteship that he vowed for [having] his son. Because the [term of naziriteship] for his son took effect before he completed his [first] term of naziriteship, it is treated as one term of naziriteship, and therefore he is unable to shave.

But if he said "I am hereby a nazirite when I will have a son", which implies a thirty-day term starting now, and he began counting his own term of naziriteship, and after that his son was born -- since he accepted the naziriteship for his son first, he sets his own [term] aside and counts his son's [term], and does not shave. Afterwards, he completes his own [term] starting from the point where he interrupted it.

A marginal note: from the Teacher: since he accepted his own term of naziriteship first, he completes his own [term] -- that is, he shaves in between [the two terms]. In the latter clause [of the Mishna], however, in which he accepted upon himself the naziriteship for his son first, the Teacher explains this as a case where, for example, his own term of naziriteship was for fifty days. He set it up this way for the following reason: if you will say that it is not so [and that it is a case where his own term was a standard term of thirty days], it would not count as a naziriteship at all, since he interrupted his own [term] and started his son's [term], and shaved, he will no longer have the opportunity for his hair to grow abundantly -- we have established in the latter clause [Nazir 15a:2] that if there is not enough time [upon restarting the count of the first term] to grow the hair, it negates the entire [term]. And if you will say: after counting [the term] for his son, let him not shave. [I will respond:] that is certainly an impossibility. For one thing, since he has accepted [the second term], it is as if he said "I am a nazirite and a nazirite", whereby he must shave between the two [terms]. And furthermore, since it says that "he sets aside his own term of naziriteship and counts that which he vowed on condition of the birth of his son" -- for what reason would he start [the term] for his son if not to be able to bring the sacrifices [at the end of that term] and to shave in between [the two terms]. And if you will say: if this clause is not about a standard term of naziriteship, but about a naziriteship of fifty days, why would it be necessary to state the other clause [Nazir 15a:2] of a naziriteship of 100 days? [I will respond:] because [the other clause] comes to teach us that "up to seventy days he has not lost anything" and that "after seventy days this negates [the first seventy days]". End of marginal note.

Gemara. Rava asks: [If one said] "I am hereby a nazirite" etc. - that is to say, it is certainly obvious to me that if he said "I am a nazirite after thirty days, and I am a nazirite" for an unspecified term, since he can complete the term of naziriteship that he said would start from now before he starts the term of naziriteship that he said would start after thirty days -- since he said "nazirite" without specifying, which is for a thirty-day term -- therefore his term of naziriteship "for now" can take effect immediately. He can shave after thirty days, and he can then count the term of naziriteship which he vowed to take after thirty days, and then shave at the end of the [second] thirty-day period. Rather, Rava asks the following: if, for example, he said "I am" etc.

Since these one hundred days are not completed within those first twenty days, they do not take effect - from now, and he is permitted to drink wine. Instead, he counts thirty days [of naziriteship] after [waiting] twenty days, and shaves, and afterwards counts 100 days.

Or perhaps since - if he starts to count the 100-day term of naziriteship immediately, he will still have enough [days] remaining to grow his hair, since there will be eighty days remaining, which is enough time to grow plenty of hair. Therefore he would be able to start counting immediately, and count twenty days, and afterwards count thirty [days of the second term], and afterwards count eight days in order to complete the first term of naziriteship.

And let him raise this dilemma with regard to a short term of naziriteship - if, for example, he said "I am a nazirite after twenty days, and an unspecified nazirite immediately". Because a thirty-day term can likewise not be completed in twenty days, it should not take effect? Or perhaps it should take effect immediately, [and he shall not shave, and for the entire twenty days he is forbidden to shave and to drink wine and to become impure by the dead. And after twenty days he counts a term of naziriteship of thirty days and does not shave. He then goes back and counts ten to complete the term of the first twenty days,] and he should shave once for both [terms].

Yes, he indeed ought to have raised that dilemma; but rather he raises one dilemma as a result of the other - that is to say, he is inquiring about one term of naziriteship within another term, and asked as follows.