Nedarim, Chapter 3, Mishnah 9. This mishnah draws a distinction between the term "yeladim" (children) and the term "noladim" (those who are born). In ordinary human speech, "yeladim" means those who have already been born, and "noladim" means those who are destined to be born afterward. In our mishnah, however, according to several of the opinions, there is a certain overlap between the two terms.
One who vows against benefit from the yeladim:
The mishnah opens with "Hanoder min hayeladim - mutar banoladim" - one who vowed not to derive benefit from the children intended, as speech ordinarily runs, those who had already been born at the time of the vow. He is therefore permitted with regard to those who had not yet been born at the time of the vow and were born afterward, and he may derive benefit from them.
One who vows against benefit from the noladim:
Here the Tannaim divide into two opinions:
The view of the first Tanna: "Min hanoladim - assur bayeladim" - even though in human speech the intention is to those who will be born in the future, the talmudic interpretation here establishes that not only those destined to be born became forbidden to him, but those who have already been born are also included in the term "noladim." It emerges that "noladim" takes in both groups together.
The view of Rabbi Meir: "Rabbi Meir matir af bayeladim" - even when he vowed against the noladim, he is permitted with regard to those who have already been born. In his approach each term is distinct and limited to itself: just as one who vows against the yeladim is permitted with regard to the noladim, so too one who vows against the noladim is permitted with regard to the yeladim.
"Vachachamim omrim: lo nitkaven zeh ela bemi shedarko leholid":
This statement of the Sages, which concludes the mishnah, was explained in the Gemara in several ways. The plain sense of the words: in saying "noladim," the one taking the vow did not specifically intend those destined to be born, but rather those types of creatures whose way it is to give birth.
Two ways of understanding their words:
A rationale for the view of the first Tanna: the Sages come to explain their position, which disagrees with Rabbi Meir. In their words, one who says "noladim" includes also those who have already been born, and not only those destined to be born. And why did he use the expression "noladim"? His entire intention was to those species that bear live young, in contrast to fish and birds, which lay eggs.
A third opinion that disagrees with both: some understand that the Sages do not come to support the position of the first Tanna, but rather disagree with the first Tanna and with Rabbi Meir alike. In their view, in both directions - whether he said "yeladim" or he said "noladim" - his vow includes both those who have already been born and those destined to be born, since his entire intention was to exclude only those that lay eggs, and nothing further.
In summary: in this mishnah we learned that one who vows against the yeladim is permitted with regard to the noladim; and regarding one who vows against the noladim they disagreed: according to the first Tanna he is forbidden even with regard to the yeladim, while Rabbi Meir permits even the yeladim. The words of the Sages, "he intended only those whose way it is to give birth," were explained either as a rationale for the view of the first Tanna, or as a third opinion according to which whichever expression he used includes both groups, and the intention of the one taking the vow is only to exclude those that lay eggs.