Nedarim, Chapter 7, Mishnah 2. Our mishnah deals with one who takes a vow against dagan (grain) and against tevuah (produce), and with the question of which species are included in each of these terms.
"Hanoder min hadagan asur b'pol hamitzri yaveish, divrei Rabbi Meir" - One who vows against dagan is forbidden dried Egyptian beans, these are the words of Rabbi Meir:
One who takes a vow against dagan, a term rendered here as grain, is forbidden even dried Egyptian beans. In the previous mishnah we noted the difference between fresh Egyptian beans, which are considered a vegetable, and dried Egyptian beans, which are not considered a vegetable; and our mishnah teaches that dried Egyptian beans are included in the term "dagan." This is the view of Rabbi Meir, who holds that the term dagan includes anything that is gathered into a keri (a heap).
"Vachachamim omrim: eino asur ela b'chameishes haminim" - And the Sages say: he is forbidden only in the five species:
According to the Sages, one who vows against dagan is not forbidden everything that is gathered into a heap, but only the five species of grain. These are the species with which one fulfills the obligation of matzah, from which bread is made, and over which one recites "Hamotzi" or "Borei minei mezonos." And they are:
Wheat.
Barley.
Oats.
Rye.
Spelt.
"Rabbi Meir omer: hanoder min hatevuah eino asur ela b'chameishes haminim" - Rabbi Meir says: one who vows against tevuah is forbidden only in the five species:
This is the view of Rabbi Meir, who is the first Tanna of the mishnah. One might have thought that the term "tevuah" is broader than the term "dagan," but Rabbi Meir establishes the opposite: the term "tevuah" is the narrower one, and it refers specifically to the five species alone.
"Aval hanoder min hadagan asur bakol, umutar b'peiros ha'ilan uvayarak" - But one who vows against dagan is forbidden everything, and is permitted fruits of the tree and vegetables:
As was established at the beginning of the mishnah, one who vows against dagan is forbidden anything that is gathered into a heap, including all kinds of legumes, the various types of beans, and the like. Fruits of the tree and vegetables, however, are permitted to him, and even though they are called tevuas hasadeh, the yield of the field, they are not included in the term "dagan."
In summary: The mishnah records a dispute about the scope of these two terms. According to the Sages, one who vows against dagan is forbidden only the five species. According to Rabbi Meir, the term "tevuah" is limited to the five species alone, while the term "dagan" is broader and includes anything that is gathered into a keri - among them dried Egyptian beans and legumes - but it does not include fruits of the tree or vegetables.