Berakhot 34B

כהן גדול, בסוף כל ברכה וברכה. והמלך, תחלת כל ברכה וברכה וסוף כל ברכה וברכה.

It is appropriate, though, for a High Priest to bow at the end of each and every blessing; and for a king to bow at the beginning of each and every blessing and at the end of each and every blessing. This is because the more lofty one’s status, the more important it is to demonstrate his subservience to God.

אמר רבי יצחק בר נחמני: לדידי מפרשא לי מיניה דרבי יהושע בן לוי: הדיוט, כמו שאמרנו. כהן גדול, תחלת כל ברכה וברכה. המלך ⁠— כיון שכרע שוב אינו זוקף, שנאמר: ״ויהי ככלות שלמה להתפלל וגו׳ קם מלפני מזבח ה׳ מכרע על ברכיו״.

R' Yitzḥak bar Naḥmani said: It was explained to me directly from R' Yehoshua ben Levi himself differently: An ordinary person, conducts himself as we said; a High Priest bows at the beginning of each and every blessing; the king, once he has bowed at the beginning of the first blessing, does not rise until he concludes the entire prayer, as it is stated: “And it was that when Solomon finished praying all of his prayer to YHWH, he rose from before the altar of YHWH, from kneeling upon his knees with his hands spread forth toward the heavens” (I Kings 8:54).

תנו רבנן: קידה ⁠— על אפים, שנאמר: ״ותקד בת שבע אפים ארץ״. כריעה ⁠— על ברכים, שנאמר ״מכרע על ברכיו״. השתחואה ⁠— זו פשוט ידים ורגלים, שנאמר: ״הבוא נבוא אני ואמך ואחיך להשתחות לך ארצה״.

Having mentioned Solomon bowing, the Talmud distinguishes between various types of bowing. A baraita states: The term kidda means bowing upon one’s face, with his face toward the ground, as it is stated: “Then Bathsheba bowed [vatikod] with her face to the ground” (I Kings 1:31). Keria means bowing upon one’s knees, as regarding Solomon it is stated: He finished praying and “he rose from before the altar of YHWH, from kneeling [mikkeroa] upon his knees.” Finally, hishtaḥava’a, that is bowing with one’s hands and legs spread in total submission, as it is stated in Jacob’s question to Joseph in response to his dream: “should we, I and your mother and your brothers, come and bow down [lehishtaḥavot] to you to the ground?” (Genesis 37:10).