If one makes a pledge in his mind to give a certain sum to charity, without ever verbalizing the pledge, does he become obligated to fulfill his promise?
The Rama (Rabbi Moshe Isserles, Poland, 1525-1572, author of glosses to the Shulchan Aruch), in the laws of Tzedaka (Yoreh Dei'a 258:13), first cites the view of the Mordechi (Rabbi Mordechai Ashkenazi, Germany, 1240-1298) that even a mental pledge constitutes a binding Neder (vow), and one must fulfill a pledge regardless of whether he verbalized it. By contrast, the Rosh (Rabbenu Asher Ben Yechiel, Germany-Spain, 1250-1327), in his responsa, held that one is not bound by a pledge unless he articulates it verbally. The Rama decides in favor of the first position, that of the Mordechi, requiring one to follow through on even mental pledges.
Halacha, however, follows the middle position, presented in the work "Dat Esh" (Siman 14), which distinguishes between entirely non-verbal pledges, and cases where only the amount of the pledge was not verbally specified. If a person verbally pledged to donate to a given cause, then even if the amount was specified only in his mind, and not verbally, he is nevertheless bound by his pledge to give the amount that he had decided upon in his mind. If, however, the pledge itself was never verbalized, then he is not bound by this pledge at all.
When one gives charity, should he afford preference to a needy Torah scholar, or to a Kohen? Kohanim are generally given preference over others with regard to Aliyot to the Torah and the like. Should they be given precedence over others when it comes to charity, as well?
Rabbi Moshe Feinstein (Russia-United States, 1895-1986), in his Iggerot Moshe (Orach Chayim, 2:34), writes that a Kohen is afforded precedence only in public contexts. Even if a certain Kohen is individually undeserving of distinction, the tribe of Kohanim does deserve respect and distinction, and therefore in public settings we give honor to the Kohen irrespective of his personal credentials. In private matters, however, such as in the distribution of charity, we weigh the Kohen's personal merits against those of the other needy individual, and therefore we award precedence to a Torah scholar over a Kohen who is not a Torah scholar.
Elsewhere in his Iggerot Moshe (Yoreh Dei'a, 4:57), Rabbi Feinstein addresses the question of whether one who makes a donation in a parent's memory should preferably donate to charity, to assist the poor, or to a Torah institution. Rabbi Feinstein rules that since "Talmud Torah Ke'neged Kulam" – the study of Torah is of equal importance to all other Mitzvot combined, it is preferable to honor one's parent's memory by supporting Torah education, rather than by donating to other worthy charitable causes.
1) A non-verbal pledge is not binding; if, however, one articulated a pledge, then even if the specific sum was decided upon only in one's mind, he is bound to give that sum.
2) When donating charity, one should give precedence to a Torah scholar in need over a needy Kohen.
3) One who wishes to make a donation in a parent's memory should preferably donate towards a Torah institution, rather than to other worthy charitable causes.