Talmud su Salmi 134:3

Rebbi Huna said: He who sees the priests in the synagogue, at the first blessing he must say (Ps. 103:20) “praise the Lord, His messengers.” At the second blessing (v. 21) “praise the Lord all His hosts.” At the third blessing (v. 22) “praise the Lord all His creatures.” At Musaf at the first blessing he must say (Ps. 134:1) “A song of ascent. Praise the Lord all servants of the Lord, who are standing in the Lord’s House in the nights.” At the second blessing (v. 2) “lift your hands in holiness.” At the third blessing (v. 3) “May the Lord bless you from Zion.” When there are four blessings then for the third he repeats the first, for the fourth the second⁶²Since the priestly blessing is regular part of the morning Amidah, the instruction on how to behave during the blessing is added here. The Babli (Soṭa 39b) gives separate verses also for days of three and four blessings and rejects the last selection of the Yerushalmi..