Nazir, Chapter Two, Mishnah Seven. In this mishnah we will examine the difference between a person who makes his nezirus conditional on the birth of a "ben" (son) and one who makes it conditional on the birth of a "vlad" (child), and the novel point the Gemara draws from each of the two halves of the mishnah.
The wording of the mishnah - one who makes his nezirus conditional on a son:
"Hareini nazir k'sheyihyeh li ben" - "I am hereby a nazir when I have a son." The person accepts nezirus upon himself on condition that a son be born to him. What is the practical ruling?
A son was born to him - the condition he stipulated has been fulfilled, and therefore "harei zeh nazir" - he is a nazir.
"Nolad lo bas, tumtum v'androginus" - a daughter, a tumtum or an androginus was born to him: "ein hu nazir" - he is not a nazir. A tumtum is one whose gender is unknown because his organs are covered over, and an androginus is one who has both organs. In all of these cases he is not a nazir, because in ordinary human speech one who says "son" means a male: not a female, and not someone whose maleness is uncertain.
One who makes his nezirus conditional on a child:
Here he did not use the word "ben" but rather "vlad" - whether he said "k'sheyihyeh vlad" (when there will be a child) or "k'sheyihyeh li vlad" (when I will have a child). In such a case, "afilu nolad lo bas, tumtum v'androginus - harei hu nazir" - even if a daughter, a tumtum or an androginus was born to him, he is a nazir, since "vlad" is a more inclusive term, covering a male, a female, and even one whose gender is not defined.
The novel point of the Gemara:
The Gemara explains what is being taught in each of the two halves of the mishnah:
In the first clause: one might have interpreted the word "ben" as related to binyan and building - as though his intention were: as long as I am built up through a child, regardless of its gender. The mishnah comes to teach that it is not to be understood that way; "ben" is meant literally - an actual son, a male.
In the final clause: the reverse is true. There was room to interpret "vlad" as referring specifically to the significant type of child, the one about whom a person says "my son." The mishnah comes to teach that this is not so; "vlad" means any type of child.
In summary: in this mishnah we learned that one who makes his nezirus conditional on the word "ben" is a nazir only if a male is born, whereas one who makes it conditional on the word "vlad" is a nazir even with a daughter, a tumtum or an androginus. The Gemara's novel point is that we do not expound "ben" as related to binyan in order to broaden it, and we do not narrow "vlad" to refer only to the significant child; rather, each of them is understood according to ordinary human speech.