"a double-edged sword in their hands, inflicting vengeance on the nations"
We're coming to the end of this series! One more difficult psalm to deal with.
There is a tension in Psalm 149, with its sharp and abrupt pivot from jubilation to judgment. Here is the celebration of the opening five verses:
Hallelujah!
Sing to the Lord a new song,
his praise in the assembly of the faithful.
Let Israel celebrate its Maker;
let the children of Zion rejoice in their King.
Let them praise his name with dancing
and make music to him with tambourine and lyre.
For the Lord takes pleasure in his people;
he adorns the humble with salvation.
Let the faithful celebrate in triumphal glory;
let them shout for joy on their beds.
This jubilation then turns toward vengeance and judgment upon the nations:
Let the exaltation of God be in their mouths
and a double-edged sword in their hands,
inflicting vengeance on the nations
and punishment on the peoples,
binding their kings with chains
and their dignitaries with iron shackles,
carrying out the judgment decreed against them.
This honor is for all his faithful people.
Hallelujah!
Historically, we can appreciate how Israel would have experienced triumph and vindication when they experienced victory or release from oppressive powers. The political worry, of course, is how Psalm 149 would be put to use (and can still be put to use) in justifying violence. This was a temptation that shows up in the Passion narratives. When the people are presented with a choice between Jesus and Barabbas, who was a violent insurrectionist/terrorist, they call for Barabbas. It's a choice we continue to face today: Jesus or Barabbas?
In light of the Incarnation, the interpretation of Psalm 149 shifts toward the cosmic and the eschatological. "For our struggle is not against flesh and blood, but against the rulers, against the authorities, against the cosmic powers of this darkness, against evil, spiritual forces in the heavens" (Eph. 6.12). On the cross Jesus "disarmed the rulers and authorities and put them to open shame, by triumphing over them" (Col. 2.15).
I wonder if the "divine council" backdrop of the Old Testament creates a bridge here. As moderns, we tend to view the conflict between Israel and the nations in a wholly disenchanted and material way. But ancient Israel saw this battle as cosmic and angelic in nature. The nations were held in thrall by malevolent "archons." Thus, "binding the kings" of the nations had a spiritual, angelic aspect. Pulling on this thread, you can see a continuity of imagination between Psalm 149 and the New Testament vision of Christ's battle with Satan, the god of this age. We go to battle with "the sword of the Spirit," the Word of God.
A sword remains in our hands, but it has been transformed.

