Kiddushin 32B

הכא תורה דיליה היא?! הדר אמר רבא: אין, תורה דיליה היא, דכתיב: ״ובתורתו יהגה יומם ולילה״.

By contrast, here, is it his Torah, that the teacher can forgo its honor? Rava then said: Yes, if he studies, it is his Torah, as it is written: “For his delight is the Torah of YHWH, and in his Torah he meditates day and night” (Psalms 1:2). This indicates that at first it is “the Torah of YHWH,” but after he studies, it becomes “his Torah.”

איני?! והא רבא משקי בי הלולא דבריה ודל ליה כסא לרב פפא ולרב הונא בריה דרב יהושע, וקמו מקמיה. לרב מרי ולרב פנחס בריה דרב חסדא, ולא קמו מקמיה. איקפד ואמר: הנו רבנן רבנן, והנו רבנן לאו רבנן?

The Talmud asks: Is that so? But Rava served drinks to the guests at his son’s wedding celebration, and he poured a cup for Rav Pappa and Rav Huna, son of Rav Yehoshua, and they stood before him when he approached them. When he poured a cup for Rav Mari and for Rav Pineḥas, son of Rav Ḥisda, they did not stand before him. Rava became angry and said: Are these rabbis, i.e., Rav Mari and Rav Pineḥas, rabbis, and are those rabbis, who stood to honor me, not rabbis? Do you think you are so great that you are not required to honor a Sage?

ותו, רב פפא הוה משקי בי הלולא דאבא מר בריה ודלי ליה כסא לרבי יצחק בריה דרב יהודה ולא קם מקמיה ואיקפד! אפילו הכי ⁠– הידור מיעבד ליה בעו.

And furthermore, it happened that Rav Pappa was serving drinks to the guests at the wedding celebration [hillula] of Abba Mar, his son, and he poured a cup for Rav Yitzḥak, son of Rav Yehuda, and he did not stand before him, and Rav Pappa became angry. These anecdotes indicate that even when a rabbi forgoes the honor due to him by serving drinks to his guests, his honor is not forgone. The Talmud answers: A rabbi can forgo the full measure of honor due to him, but even so, others are required to perform some act of reverence, such as preparing to stand before him.