KESUVOS 50 - Two weeks of study material have been dedicated by Mrs. Estanne Abraham Fawer to honor the Yahrzeit of her father, Rav Mordechai ben Eliezer Zvi (Rabbi Morton Weiner) Z'L, who passed away on 18 Teves 5760. May the merit of supporting and advancing Dafyomi study -- which was so important to him -- during the weeks of his Yahrzeit serve as an Iluy for his Neshamah.

The Gemara relates that the Rabanan of Usha instituted that one should not give away more than one fifth of his assets to Tzedakah, because doing so might cause him to become impoverished. It seems that one is permitted to give away up to a fifth, but one is not required to do so.
The CHAFETZ CHAYIM discusses many points of this Halachah in SEFER AHAVAS CHESED (chapters 19-20).
1. Although one is not required to give more than a tenth of his income to Tzedakah (see TOSFOS to Ta'anis 9a), the Chafetz Chayim (ch. 19) writes that a person who wants to give Tzedakah generously should give one fifth of his income, as Yakov Avinu did (Bereishis 28:22).
When a person gives a fifth of his money to Tzedakah he should not give it all at once, but he should divide it into two tenths, as the verse implies. The SHITAH MEKUBETZES gives a number of reasons for this. First, it accustoms a person towards giving, as the RAMBAM writes in Avos (3:15) that it is better to give one coin a thousand times than a thousand coins at one time.
Second, the Shitah Mekubetzes writes in the name of the ME'IRI that it is proper to divide it into two tenths in order to parallel the two Ma'aseros that are given from fruits of fields in Eretz Yisrael. Every year two Ma'aseros are separated -- Ma'aser Rishon and Ma'aser Sheni (or Ma'aser Ani). Since the two tenths parallel the two Ma'aseros, it is appropriate that one tenth, which corresponds to Ma'aser Sheni, may be invested in any Mitzvah. It may even be invested in a Mitzvah from which one benefits personally, such as writing a Sefer Torah or buying Sefarim to lend out, similar to Ma'aser Sheni which is eaten by the owner himself in Yerushalayim. The other tenth, which corresponds to the Ma'aser that is given to Kohanim and Leviyim, should be distributed as Tzedakah to the poor. The Chafetz Chayim adds that since it corresponds to the Ma'aser that is distributed to the Kohanim and Leviyim, it should be given to needy Talmidei Chachamim, as the verse refers to the tribe of Levi as those who teach the Torah (Devarim 33:10).
(Besides these reasons, the Chafetz Chayim points out that it is important to separate Tzedakah in tenths for Kabalistic reasons.)
2. The Chafetz Chayim adds that there are situations in which one is required, and not just encouraged, to give a fifth of one's earnings to Tzedakah. Based on the RAMBAM (Perush ha'Mishnayos to Pe'ah 1:1) and on the VILNA GA'ON in his letter, ALIM L'TERUFAH, the Chafetz Chayim asserts that the Gemara here is discussing a person who separates money for Tzedakah before he has a particular Tzedakah to which to give it, and he is looking for ways in which to use the money for Tzedakah. (This is implicit in the Gemara's expression "ha'Mevazbez.") If, however, a person knows of a specific poor man who is in need of help, he is obligated to help the poor man even if it requires separating up to a fifth of his earnings.
Although the Chachamim in Usha prohibited one from distributing more than a fifth of one's money to Tzedakah, the Chafetz Chayim (ch. 20) writes that a person sometimes is permitted to give even more than a fifth of his earnings to Tzedakah.
1. When there are poor people whom one knows are in need, he is obligated to give up to one fifth of his money to help them (see above). The Chafetz Chayim bases this ruling on the words of the Rambam. One is permitted to give even more than a fifth of one's money in such a situation (see Insights to Ta'anis 24:1).
2. An exceptionally wealthy person is permitted to give more than a fifth of his money to Tzedakah, since doing so will most likely not cause him to become impoverished (based on TOSFOS to Bava Kama 9b, DH Ileima).
3. If a person is a Shechiv Mera (on his deathbed) and expects to die very soon and thus does not have to worry about becoming impoverished, he may distribute even more than a fifth of his money (but not all of it) to Tzedakah (based on the RABEINU YONAH, cited by the Shitah Mekubetzes, who cites the Gemara in Kesuvos 67b).
4. The Chafetz Chayim writes that the prohibition of the Rabanan of Usha perhaps applies only to a person who gives away a large sum of money at once from his estate (as the word "Mevazbez" implies). Is one permitted, though, to calculate how much he needs for his weekly income (and other needs) and to set aside the rest for Tzedakah, even if that extra amount is more than a fifth? Perhaps in such a situation there is no concern that he will become impoverished and have to beg for food, since he makes sure to leave enough money to support himself. The Chafetz Chayim concludes that in such a case one indeed is permitted to give away more than a fifth of his earnings.
5. The Chafetz Chayim writes that if a person wants to enter into a "Yisachar-Zevulun" arrangement by supporting a Talmid Chacham with even more than a fifth of his earnings, he is permitted to do so, as the Gemara implies in a number of places (see, for example, Sotah 21a, and Rashi there, DH Shimon). Similarly, the Shitah Mekubetzes writes that one is permitted to support Bnei Torah with more than a fifth of one's money, as was the conduct of Rebbi Akiva as cited in the Midrash Rabah (Vayikra 34:16) to Parshas Behar.
The Chafetz Chayim explains that a "Yisachar-Zevulun" agreement is not simply a distribution of Tzedakah; it is a formal business deal whereby one invests his money in the Torah in order to share in the reward of the one learning. That is why one is permitted to make such a deal even with more than a fifth of one's possessions.