Rosh Hashanah 14B

אחד כדברי בית שמאי, ואחד כדברי בית הלל.

One tithe was in accordance with the statement of Beit Shammai that the new year for trees is on the 1st of Shevat, in which case it was already the third or 6th year, when one must set aside poor man’s tithe; and one tithe was in accordance with the statement of Beit Hillel that the new year for trees is on the 15th of Shevat, so it was still the second or 5th year, when one must set aside second tithe.

רבי יוסי בר יהודה אומר: לא מנהג בית שמאי ובית הלל נהג בה, אלא מנהג רבן גמליאל ורבי אליעזר נהג בה.

R' Yosei bar Yehuda says: He did not act as he did in order to conform with the conflicting practices of Beit Shammai and Beit Hillel. Rather, he acted as he did in order to conform with the conflicting practices of Rabban Gamliel and R' Eliezer.

דתנן: אתרוג שוה לאילן בשלשה דרכים, ולירק בדרך אחד. שוה לאילן בשלשה דרכים: לערלה ולרבעי ולשביעית ולירק בדרך אחד ⁠— שבשעת לקיטתו עישורו, דברי רבן גמליאל.

As we learned in a Mishnah: The etrog tree is like an ordinary tree in 3 ways and like a vegetable in one way. How so? It is like an ordinary tree in 3 ways: With regard to orla, that the fruit of the first 3 years after the tree is planted is forbidden; with regard to 4th-year produce, that the fruit that grows in the 4th year after the tree is planted must be brought to Jerusalem and eaten there or else it must be redeemed; and with regard to the Sabbatical Year, that the year is determined by the time of the formation of its fruit. And the etrog is like a vegetable in one way, which is that its tithe year follows the time of the picking of its fruit; this is the statement of Rabban Gamliel.