1 Behold, bless ye the LORD, all ye servants of the LORD, which by night stand in the house of the LORD. 2 Lift up your hands in the sanctuary, and bless the LORD. 3 The LORD that made heaven and earth bless thee out of Zion.
People sit when they disparage, but they stand when they bless the Lord, to whom it is said, “Behold, now bless you the Lord, all you servants of the Lord, who stand in the house of the Lord.” One who sits (to speak of the bodily habit) is, as it were, unnerved, when the body is idle and when he relaxes the tension of his mind. But a cautious watchman, an active searcher, a wide-awake guard before the camp, stands. The soldier on duty, who wishes to anticipate the enemy’s designs, stands in the battle line before he is expected.
"Behold, now, bless ye the Lord, all you servants of the Lord" [Psalm 134:1], "who stand in the house of the Lord, in the courts of the house of our God" [Psalm 134:2]. Why has he added, "in the courts"? Courts mean the wider spaces of a house. He who stands in the courts is not straitened, is not confined, in some fashion is enlarged. Remain in this enlargement, and you can love your enemy, because you love not things in which an enemy could straiten you. How can you be understood to stand in the courts? Stand in charity, and you stand in the courts. Breadth lies in charity, straitness in hatred.
But notice what “Lift up” means: “Give alms more generously,” for the Lord not only demands pious words from us, but also deeds. He added, “in the sanctuary,” so that the hand of a Christian may produce the alms. For if heretics or pagans give alms, their hands are not lifted up in the sanctuary, inasmuch as Christ accepts only those very alms that a faithful Christian offers to his name. Nonetheless, lest someone arrogate anything to himself, he says that one ought to bless the Lord while doing this act, since he himself grants both a merciful mind and abundant wealth. Thus he teaches that the love of the Lord ought to be fulfilled with sacred praises and pious deeds. When these things have been accomplished, see how a worthy reward follows.
"Lift up your hands by night in the sanctuary, and bless the Lord" [Psalm 134:2]. It is easy to bless by day. What is "by day"? In prosperity. For night is a sad thing, day a cheerful. When it is well with you, thou dost bless the Lord. Your son was sick, and he is made whole, thou dost bless the Lord. Your son was sick, perchance you have sought an astrologer, a soothsayer, perchance a curse against the Lord has come, not from your tongue, but from your deeds, from your deeds and your life. Boast not, because you bless with your tongue, if you curse with your life. Wherefore bless ye the Lord. When? By night. When did Job bless? When it was a sad night. All was taken away which he possessed; the children for whom his goods were stored were taken away. How sad was his night! Let us however see whether he blesses not in the night. "The Lord gave, the Lord has taken away; it is as the Lord willed; blessed be the name of the Lord." [Job 1:21] And black was the night....
"The Lord out of Zion bless you, who made heaven and earth" [Psalm 134:3]. He exhorts many to bless, and Himself blesses one, because He makes one out of many, since "it is good and pleasant for brethren to dwell together in one." It is a plural number, brethren, and yet singular, to dwell together in one. Let none of you say, It comes not to me. Do you know of whom he speaks, "the Lord bless you out of Zion." He blessed one. Be one, and the blessing comes to you.
[AD 397] Ambrose of Milan on Psalms 134:1-2