Les Psaumes 146:8 Halakha : Mishneh Torah, Prayer and the Priestly Blessing & Kitzur Shulchan Arukh

Genuflection. The worshiper bends the knees five times in every [Amidah] prayer,^*Prayer, recited standing. at the beginning and at the end of the first blessing; at the beginning and the end of the thanksgiving blessing (which begins "We thank Thee"); and after the conclusion of the prayer. The knees are then bent, the worshiper steps backwards three paces, and with knees bent, bows to the left, then to the right, and then raises his head. When he bends the knees the first four times, he does so while uttering the word "Blessed" and resumes the erect posture at the word "O Lord." This rule applies to the layman. The high priest however bends the knees at the beginning and end of every blessing. The king bows his head at the beginning of the [Amidah] prayer and does not raise it till he has concluded it.

When he hears the crowing of the cock, he recites the blessing, "Blessed art Thou, O Lord our God, King of the Universe^*This sentence “Blessed … Universe” precedes every one of the following blessings., who hast given to the cock intelligence to distinguish between day and night." When he puts on his garments, he recites, "Blessed art Thou, O Lord our God, King of the Universe, who clothest the naked." When he puts on his headgear he recites, "Blessed art Thou, O Lord our God, King of the Universe, who crownest Israel with glory." When he passes his hands over his eyes, he recites, "Who openest the eyes of the blind." When he sits up on his couch, he recites, "Who loosest those that are bound." When he descends from the couch and puts his feet on the ground, he recites, "Who spreadest forth the earth above the waters". When he stands up, he recites, "Who raisest up them that are bowed down". When he washes his hands, he recites, "Who hast sanctified us by Thy commandments and given us a command concerning the washing of the hands". When he washes his face, he recites the blessing, "Blessed art Thou, O Lord our God, King of the Universe, who removest the bands of sleep from mine eyes and slumber from mine eyelids. May it be Thy will, O Lord my God and God of my fathers to accustom me to religious duties and not accustom me to transgression. Let the good inclination have sway over me and let not the evil inclination have sway over me. Strengthen me in Thy commandments and grant my portion in Thy Law. Grant that I may be vouchsafed grace, loving kindness and mercy in Thy sight and in the sight of all who behold me, and bestow upon me loving kindnesses. Blessed art Thou, O Lord, who bestowest loving kindnesses upon Thy people, Israel.

You must bend your knees and bow four times during the Shemoneh Esrei, at the beginning of the first berachah and at its conclusion,³⁵The berachah which ends with the words Magein Avrohom is the conclusion of the first berachah. and at the berachah of Modim, at its beginning and end.³⁶The berachah ending with the words Hatov shimecha ulecha naeh lehodos is the conclusion of Modim. When saying Baruch, bend your knees; and when you say atah bow until the vertebrae of the spinal column protrude, and you must also bow your head. Before pronouncing the Name [Hashem],³⁷The Shulchan Aruch states that one should straighten up as he says Hashem. straighten up slowly (as it is said;) "Hashem straightens the bent."³⁸Psalms 146:8. Similarly, when saying Modim, bend your knees and bow,³⁹Our custom, however, is not to bend the knees when saying Modim. and before pronouncing the Name [Hashem], you should straighten up. Do not bend too low, so that your mouth is opposite your belt, because this is an act of ostentation. For an old person or an invalid to whom bending the knees is painful, just nodding the head is sufficient. It is forbidden to bow additionally at the other berachos, either at their beginning or their end.