‘God takes pleasure in people.’ (4)
This is the penultimate psalm in the book, short and bitter-sweet. Four verses of praise, singing and dancing, including the important statement of love quoted above; four verses of wreaking vengeance on enemies; and in the middle, it appears, a good lie down!
Let the faithful rejoice in triumph; let them be joyful on their beds. (5)
An odd little verse, and indeed it struck Isaac Everett to the point that he chose this for his responsive refrain. He wonders whether it implies that the people routinely slept in the Temple, that praise at home as well as in the Temple is fine, or perhaps just relishing being in bed.1
Despite its central location, the bed verse is not the key to the song and its use as the refrain seems a little idiosyncratic. Scanning for meaningful and respectful ways to praise in song, verse 1 is a better bet:
Sing to God a new song; sing praise in the congregation of the faithful.

A little further on there’s a nice statement of why psalm tragics do this:

… sing praise making melody with timbrel and lyre; for God takes pleasure in people and adorns the poor with victory. (3, 4)
The NRSV translation of verse 4 says: “the Lord takes pleasure in his people”. Removing the male gender bias, one has the line quoted above. This to me seems more powerful; do we not all, if made in the image of this God, take pleasure in people? Whether a correct reading or not, it also broadens the focus from the ‘chosen people’, the Israelites, to the whole of humanity.
The second half of the psalm is less comfortable. ‘Wreak vengeance on the nations and punishment on the people … inflicting judgment.’ (7) Is not this just the sort of cry we, well, decry when it leads to the extremist religious violence that seems increasingly to dominate the news? Remember that the historical reference is to the Exodus and the early opposed establishment of Israel, which was a fight for survival.
Today, in the light of the New Testament modifier to love your enemies, the reader regards it metaphorically. Most commentators see it now as a fight against evil. Any enthusiasm for holy war against other people sounds bizarre. For as we just saw, God takes pleasure in people.
A cautionary note on this passage in PFAS says: ‘It is, then, a psalm to handle with great care.’ However, the note continues that the psalm is instructive about the nature of faithful obedience in a world of injustice.2 The psalm again encourages the fight for justice and equity, for ‘God loves people’ as we do, and ‘adorns the poor’, as we should. Tom Wright has this insight relating to both 148 and 149:
To put it in modern shorthand, you find the political message within the ‘creational’ message. Once you summon the whole of creation to praise the maker, you can begin to see clearly where the fault lines lie within the world of human power.3
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Bach wrote two impressive works on this psalm, both entitled Singet dem Herrn. BWV190 is an lengthy cantata written for New Year’s Day in Leipzig in 1724. BWV 225, sung here by the Netherlands Bach Society, is scored for double choir. Both are demanding works for amateur singers.
The Everett refrain has already been mentioned. PFAS has a nice responsive setting (149B) with a contemporary sound even though the music was written back in the 18th century.
TiS 95 has a good setting by reliably valued Sydney-born composer Christopher Willcock SJ. The response is simple, and the stacked triads of the tone (the simple tune for the verses) is enticing. It only presents half the lectionary, however, and ducks that confronting second section discussed above. Our recorded CoviDeo adds the last verse:
Bringing all evil to justice this is glory for the faithful.
If you really want to sing of vengeance upon the forces opposing a rule of love, try a solo by Catalan composer and contemporary of Bach, Francisco Valls. Best with its original figured bass, the sharper edges are modestly veiled in Latin:

1 TEP page 275
2 Psalms for All Seasons, page 989 footnote.
3 Wright, N T, Finding God in the Psalms, page 150-1