Megillah 5B

ורחץ בקרונה של צפורי בשבעה עשר בתמוז, ובקש לעקור תשעה באב ⁠— ולא הודו לו.

And he bathed at the time when the wagons [kerona] were traveling through Tzippori, i.e., on the market day, when the public would know about it, on the 17th of Tammuz, to show that bathing is permitted on that day. And he sought to abolish the fast of the 9th of Av. And with respect to the 9th of Av, the rabbis did not agree with him.

אמר לפניו רבי אבא בר זבדא: רבי, לא כך היה מעשה. אלא תשעה באב שחל להיות בשבת הוה, ודחינוהו לאחר השבת. ואמר רבי: הואיל ונדחה ⁠— ידחה, ולא הודו חכמים. קרי עליה: ״טובים השנים מן האחד״.

R' Abba bar Zavda said to R' Elazar: my teacher! the incident did not occur in this fashion. R' Yehuda HaNasi never sought to abolish the fast of the 9th of Av. Rather, it was a year when the 9th of Av occurred on Shabbat, and they postponed it until after Shabbat. And R' Yehuda HaNasi said about that case: Since it has already been deferred from its usual time, let it be altogether deferred this year. And the Rabbis did not agree with him. R' Elazar read the verse about R' Abba bar Zavda: “Two are better than one” (Ecclesiastes 4:9), meaning, it is good that you were here to provide an accurate report about that incident.

ורבי היכי נטע נטיעה בפורים? והתני רב יוסף: ״שמחה ומשתה ויום טוב״, ״שמחה״⁠ — מלמד שאסורים בהספד, ״משתה״⁠ — מלמד שאסור בתענית, ״ויום טוב״⁠ — מלמד שאסור בעשיית מלאכה! אלא: רבי, בר ארביסר הוה, וכי נטע ⁠— בחמיסר נטע.

The Talmud asks: And how could R' Yehuda HaNasi plant a sapling on Purim? Didn’t Rav Yosef teach with regard to the verse: “Therefore the Jews of the villages, who reside in the unwalled towns, make the 14th day of the month of Adar a day of gladness and feasting, and a good day [yom tov]” (Esther 9:19), that the term “gladness” teaches that it is prohibited to eulogize on Purim; “feasting” teaches that it is prohibited to fast; and the term “good day” [yom tov] teaches that it is prohibited to perform labor, just as on a Festival, which is also referred to as a yom tov? Rather, what happened was as follows: R' Yehuda HaNasi was in a place that observed Purim on the 14th, and when he planted the sapling, he planted it on the 15th.