If a man takes a vow to become a nazir "from here until the end of the world" he is only obligated to follow the rules of nezirut for a thirty-day period. This period is the time frame for any vow of nezirut made without a specific designation of duration. The gemara explains this rule of the mishna as follows: We interpret his statement as an expression of anguish, that the thirty-day abstention period is as difficult for him as if it would be the 500 years which our Sages tell us it takes a man to traverse the universe by foot.

In a later mishna (8a) we learn that a man who makes a vow to observe nezirut "like the hairs of his head" is obligated to repetitively observe thirty-day periods of nezirut, cutting his hair and bringing sacrifices at the conclusion of each period, and starting all over again. We look upon his declaration as a commitment to observe as many nezirut periods as there are hairs on his head. But when he makes a vow for a hundred or a thousand years of nezirut, he must observe one long period of nezirut for the rest of his lifetime.

What emerges from the above is a clear distinction between a vow made with hairs as the standard and one made with days. In the former case we view each hair as a separate unit so that he is seen as accepting an innumerable number of nezirut periods, while in the latter cases we view the days as one long unit. (Why we take a lenient approach to "from here until the end of the world" and a strict approach to a commitment of 100 or 1000 years is explained in the gemara on the basis of his use of the term "until the end of the world" rather than specifying 500 years.)

As an explanation of this distinction, the Sage Rabba states that hairs are separated from each other while time is a continuum. But days too are considered separate units, challenges the gemara, as we see in the Torah's description of the first day of creation: "It was evening and it was morning -- one day" (Bereishet 1:8). Rabba's response was that the intention of that passage was to establish that the night precedes the day in the structure of a 24-hour period, a consideration with ramifications for the observance of Shabbat and Festivals. It does not communicate any concept of days being actually separated from one another.

An interesting explanation of this concept of time continuum is offered by Rabbi Zvi Hirsch Chayot. Whenever it is day in one part of the world it is night somewhere else, so there is no real separation even between night and day as there is in the case of hair.

Nazir 7a

How is it possible for a Jew with no hereditary disqualification to be forbidden to marry a Jewish woman? If he appointed an agent to take a wife for him through kiddushin but did not specify any particular woman. Should that agent die before reporting to him on the details of the mission -- which we assume he carried out -- his sender is forbidden to marry any Jewish woman because she may be the sister, mother or daughter of the woman whom the agent made his wife.

The question arises: If we thus assume that an agent carries out his mission and that he made some woman his sender's wife, it should follow that no Jew can marry any woman, for she may be that mysterious woman who is already betrothed to the sender. Tosefot raises this problem and cites the solution proposed by Rabbeinu Tam, that every woman is believed to declare that the agent did not make kiddushin with her. (In Mesechta Gittin 64a, Tosefot says that it is unlikely that a woman who had been made the sender's wife by the agent would accept kiddushin from another man. It is safe to assume that this is the basis for Rabbeinu Tam's approach for granting credibility to a woman regarding her marital status.)

But Rabbeinu Tam's solution will not cover the girl whose father died when she was a minor. He may well have accepted kiddushin from the agent and made her the sender's wife without her knowledge. The subsequent death of the father before divulging to her that she is a married woman would make her forbidden to all men.

Tosefot's conclusion is that as far as Torah law is concerned, neither the sender nor anyone else should be affected in regard to the range of their marital opportunities by the mystery created through the agent's action. This is so because we can apply the classic rule of majority indication and conclude that any particular woman is a member of the majority of women in the world who are neither this mysterious object of the agent's kiddushin nor any of her close relatives. It is only the sender himself, who acted irresponsibly in delegating an agent in a manner that could create such a mystery, whom the Sages penalized by prohibiting him to marry anyone. They did not extend this penalty to others who can rely on majority indication.

Even regarding the sender himself, if at the time he appointed the agent all of the close relatives of the woman he now wishes to marry were themselves married, we can assume that the agent did not act to make any of them his sender's wife, and he may therefore marry this woman.

Nazir 12a