Biblical Commentary on the Old Testament, by Carl Friedrich Keil and Franz Delitzsh, [1857-78], at sacred-texts.com
Night-Watch Greeting and Counter-Greeting
This Psalm consists of a greeting, Psa 134:1-2, and the reply thereto. The greeting is addressed to those priests and Levites who have the night-watch in the Temple; and this antiphon is purposely placed at the end of the collection of Songs of degrees in order to take the place of a final beracha. In this sense Luther styles this Psalm epiphonema superiorum. It is also in other respects (vid., Symbolae, p. 66) an appropriate finale.
The Psalm begins, like its predecessor, with הנּה; there is directs attention to an attractive phenomenon, here to a duty which springs from the office. For that it is not the persons frequenting the Temple who are addressed is at once clear from the fact that the tarrying of these in the Temple through the night, when such a thing did actually occur (Luk 2:37), was only an exception. And then, however, from the fact that עמד is the customary word for the service of the priests and Levites, Deu 10:8; Deu 18:7; Ch1 23:30; Ch2 29:11 (cf. on Isa 61:10, and Psa 110:4), which is also continued in the night, Ch1 9:33. Even the Targum refers Psa 134:1 to the Temple-watch. In the second Temple the matter was arranged thus. After midnight the chief over the gate-keepers took the keys of the inner Temple and went with some of the priests through the little wicket of the Fire Gate (שׁער בית המוקד). In the inner court this patrol divided into two companies, each with a burning torch; one company turned west, the other east, and so they compassed the court to see whether everything was in readiness for the service of the dawning day. At the bakers' chamber, in which the Mincha of the high priest was baked (לשׁכת עשׂי הביתין), they met with the cry: All is well. In the meanwhile the rest of the priests also arose, bathed, and put on their garments. Then they went into the stone chamber (one half of which was the place of session of the Sanhedrim), where, under the superintendence of the chief over the drawing of the lots and of a judge, around whom stood all the priests in their robes of office, the functions of the priests in the service of the coming day were assigned to them by lot (Luk 1:9). Accordingly Tholuck, with Kster, regards Psa 134:1. and Psa 134:3 as the antiphon of the Temple-watch going off duty and those coming on. It might also be the call and counter-call with which the watchmen greeted one another when they met. But according to the general keeping of the Psalm, Psa 134:1. have rather to be regarded as a call to devotion and intercession, which the congregation addresses to the priests and Levites entrusted with the night-service in the Temple. It is an error to suppose that "in the nights" can be equivalent to "early and late." If the Psalter contains Morning Psalms (Psa 3:1-8, Psa 63:1-11) and Evening Psalms (Psa 4:1-8, Psa 141:1-10), why should it then not contain a vigil Psalm? On this very ground Venema's idea too, that בּלּילות is syncopated from בּהלּילות, "with Hallels, i.e., praises," is useless. Nor is there any reason for drawing ἐν ταῖς νυξίν, as the lxx does, to Psa 134:2,
(Note: The lxx adjusts the shortening of Psa 134:1 arising from this, by reading בחצרות בית אלהינו העמדים בבית ה after Psa 135:2.)
or, what would be more natural, to the בּרכוּ that opens the Psalm, since it is surely not strange that, so long as the sanctuary was standing, a portion of the servants of God who ministered in it had to remain up at night to guard it, and to see to it that nothing was wanting in the preparations for the early service. That this ministering watching should be combined with devotional praying is the purport of the admonition in Psa 134:2. Raising suppliant hands (ידכם, negligently written for ידיכם) towards the Most Holy Place (τὰ ἅγια), they are to bless Jahve. קדשׁ (according to B. Sota 39a, the accusative of definition: in holiness, i.e., after washing of hands), in view of Psa 28:2; Psa 5:8; Psa 138:2 (cf. רום in Hab 3:10), has to be regarded as the accusative of the direction.
Calling thus up to the Temple-hill, the church receives from above the benedictory counter-greeting: Jahve bless thee out of Zion (as in Psa 128:5), the Creator of heaven and earth (as in Psa 115:15; Psa 121:2; Psa 124:8). From the time of Num 6:24 jebaréchja is the ground-form of the priestly benediction. It is addressed to the church as one person, and to each individual in this united, unit-like church.