Sanhedrin 100A

לא שרו לן עורבא, ולא אסרו לן יונה.

have they permitted a raven for us nor have they prohibited a dove for us. They merely tell us matters stated explicitly in the Torah.

רבא, כי הוו מייתי טריפתא דבי בנימין קמיה, כי הוה חזי בה טעמא להיתירא, אמר להו: תחזו דקא שרינא לכו עורבא. כי הוה חזי לה טעמא לאיסורא, אמר להו: תחזו דקא אסרנא לכו יונה.

The Talmud relates with regard to Rava: When they would bring a possible tereifa from the house of Binyamin before him, when he would see in it a reason to permit its consumption, Rava would say to them: See that I am permitting a raven for you, as this is an animal that appeared forbidden. When he would see in it a reason to prohibit its consumption, Rava would say to them: See that I am prohibiting a dove for you.

רב פפא אמר: כגון דאמר ״הני רבנן״. רב פפא אישתלי ואמר: ״כגון הני רבנן״, ואיתיב בתעניתא.

Rav Pappa says: The epikoros mentioned in the Mishnah is referring to one who conducts himself like one who says: Those rabbis, with contemptuous overtones. The Talmud relates that Rav Pappa himself forgot in one instance and said: Like those rabbis, and he observed a fast to achieve atonement for expressing himself in that manner.

לוי בר שמואל ורב הונא בר חייא הוו קא מתקני מטפחות ספרי דבי רב יהודה. כי מטו מגילת אסתר אמרי: הא [מגילת אסתר] לא בעי מטפחת. אמר להו: כי האי גוונא נמי מיחזי כי אפקירותא.

The Talmud relates: Levi bar Shmuel and Rav Huna bar Ḥiyya were mending mantles for the sacred scrolls of the school of Rav Yehuda. When they reached the scroll of Esther they said: This scroll of Esther does not require a mantle, as it is not as significant as the other sacred scrolls. Rav Yehuda said to them: A statement of that sort also seems to express irreverence like the irreverence typical of an epikoros, as you should not have referred to the scroll of Esther as: This scroll.