Reference for Ketubot 99:2

א"ר אילעא באושא התקינו המבזבז אל יבזבז יותר מחומש תניא נמי הכי המבזבז אל יבזבז יותר מחומש שמא יצטרך לבריות ומעשה באחד שבקש לבזבז [יותר מחומש] ולא הניח לו חבירו ומנו רבי ישבב ואמרי לה רבי ישבב ולא הניחו חבירו ומנו רבי עקיבא

R. Elai stated: It was enacted at Usha that if a man wishes to spend liberally he should not spend more than a fifth. It was also taught: If a man desires to spend liberally he should not spend more than a fifth, lest he come to need the help of people. And it once happened that a man wished to spend more than a fifth but his friend did not allow him. Who was it? R. Yeshevav. Others say [that the man who wished to spend was] R. Yeshevav, but his friend did not allow him. And who was it? R. Akiva.

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