Kesubos 50a: One should not give more than one fifth of his income to tzedaka.
כתובות נ ע”א: א״ר אילעא: באושא התקינו, המבזבז ־ אל יבזבז יותר מחומש.
Rabbi Eliyahu Chaim Meisel, the Rav of Lodz, was known to give any money he had to tzedakah. They asked him, “Rebbe, how can you give away so much money for tzedakah? It says that a person is not allowed to give away more than one fifth.”
The Rav answered, “You are right. It is a terrible aveirah, and I was always very careful not to give away more than one fifth. However, one day I accidentally gave away more than one fifth. I did not know what to do. How could I gain atonement for this sin? I took the advice that Daniel gave to Nevuchadnetzar: Giving tzedakah will atone for your sin (Daniel 4:24). So I gave tzedakah to be mechaper for giving more than one fifth. Then I realized I did another aveirah by giving more than one fifth again, so I needed to give more tzedakah. I needed to keep giving away my money for tzedakah as an atonement until I had no more money left, and would be potur as an oneis.”
When he met Rabbi Chaim Ozer Grodzenski, Reb Eliyahu Chaim praised his recently published sefer, Achiezer. Reb Chaim Ozer asked Reb Eliyahu Chaim, “When will you write a sefer?”
Reb Eliyahu Chaim pulled out promissory notes from his pockets for loans he had signed for and said, “This is my sefer. I am so busy with tzedakah that I don’t have time to write a sefer.”
“My sefer pales in comparison to yours,” Reb Chaim Ozer declared.
Source: Mah Nomar, Hilchos Chol Hamoed, p. 44
[Notwithstanding his humorous answer, it would seem that Reb Eliyahu Chaim did have a legitimate reason for giving away more than one fifth. The reason why one is not allowed to give more than a fifth is because we are afraid he himself will become poor and will be a burden on others. As the Rav, Reb Eliyahu Chaim held it was the obligation of the people to support the poor. He would borrow and give to the poor, and he was famous for paying the Russian government’s fees to exempt boys from the draft. The community had the obligation to reimburse him because he was really distributing the tzedaka on their behalf.]
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