Yoma 53B

אמרו ליה לרב יוסף: הכי עביד רבא. אמר ליה: יהא רעוא דתרום רישך אכולה כרכא.

They said to Rav Yosef: This is what Rava does. Rav Yosef was blind and could not see for himself. Rav Yosef said to him: May it be God’s will that you lift your head over the entire city, in reward for honoring your teacher.

אמר רבי אלכסנדרי אמר רבי יהושע בן לוי: המתפלל, צריך שיפסיע שלש פסיעות לאחוריו, ואחר כך יתן שלום. אמר ליה רב מרדכי: כיון שפסע שלש פסיעות לאחוריו ⁠— התם איבעיא ליה למיקם. משל לתלמיד הנפטר מרבו, אם חוזר לאלתר, דומה לכלב ששב על קיאו.

§ Apropos the obligation of a student to walk backward when taking leave of his teacher, the Talmud discusses a similar topic. R' Alexandri said that R' Yehoshua ben Levi said: One who prays must take 3 steps backward upon concluding his prayer and then recite: Peace, in a manner befitting one who departs from before God. Rav Mordekhai said to him: Since he has taken 3 steps backward, he should stand there and not return to his place immediately. This is analogous to a student who takes leave of his teacher. If he returns immediately to the place where was first standing, he is similar to a dog who returns to its vomit, and his previous action is spoiled.

תניא נמי הכי: המתפלל, צריך שיפסיע שלש פסיעות לאחוריו ואחר כך יתן שלום, ואם לא עשה כן ראוי לו שלא התפלל. ומשום שמעיה אמרו: שנותן שלום לימין, ואחר כך לשמאל, שנאמר: ״מימינו אש דת למו״, ואומר: ״יפול מצדך אלף ורבבה מימינך״.

The Talmud comments that this was also taught in a baraita: One who prays must take 3 steps backward upon concluding his prayer and then recite: Peace. And if he did not do so, it is better for him not to have prayed, as his actions are disrespectful toward God. And they said in the name of Shemaya the Sage that when one recites: Peace, he first bows to the right and then to the left, as it is stated: “At His right hand was a fiery law to them” (Deuteronomy 33:2), and it says: “1,000 may fall at your side, and 10,000 at your right side” (Psalms 91:7).