The benefit of discretion-tovat hana-ah- טוֹבַת הֲנָאָה TB Nedarim 84a

 The Mishnah on daf TB Nedarim 83a teaches “If a woman vowed: The property of other people is konam for me, and for that reason I will not benefit from it, her husband cannot nullify her vow, but nevertheless, if she is poor, she may benefit from the agricultural gifts that must be left for the poor: Gleanings, i.e., isolated stalks that fell during the harvest; forgotten sheaves; and produce of the corners [pe’a] of the field that the owner is obligated to leave for the poor. Enjoyment of these gifts is not considered as benefit derived from people, as these gifts are not given voluntarily out of the kindness of the donors, but in the performance of a mitzva.” (Sefaria.org translation) on TB Nedarim 84 there is a tannaitic disagreement whether she may benefit from ma’aser oni (מַעְשַׂר עָנִי).

To refresh your memory, a farmer in Israel gives terumah to the kohen which equals 2% of his crop. Then he gives ma’aser rishon (the first tithe) to the Levite which equals the next 10% of his crop. In years one, two, four, and five in the seven-year cycle, the farmer takes ma’aser sheni, the next 10% of his crop and enjoys it in Jerusalem. In years three and six, the same 10% of his crop is given to the poor as ma’aser oni.

The tannaitic disagreement whether she may benefit from ma’aser oni (מַעְשַׂר עָנִי) revolves around the principle “the benefit of discretion-tovat hana-ah-טוֹבַת הֲנָאָה).” According to her vow she cannot benefit directly from anybody. Rav Yosef explains that the debate about ma’aser oni is whether a person has to designate the poor person he is given to or whether he can just leave it for any poor person. The sages hold he has the benefit of discretion-tovat hana-ah-טוֹבַת הֲנָאָה, then this woman who took the above vow would not be able to benefit from his ma’aser oni. Rabbi Eliezer holds the farmer leaves the ma’aser oni ownerless like the gleanings, the forgotten sheaves, and the corners of the fields, she may benefit from it because it is indirect distribution.

Rav’s solution to harmonize the disagreement by saying the sources are describing are two different distribution centers of ma’aser oni. The first distribution center is your house where you give this tithe directly to the poor. Obviously, since this is direct distribution, the woman may not benefit from this distribution center. The second distribution center is the granary. The grain is just there for any poor person to take. Obviously, this is indirect distribution just like gleanings, the forgotten sheaves, and the corners of the fields, she may benefit from it.