The psalm opens with a scene: by the waters of Babylon, there we sat down and wept, when we remembered Zion. The exiles hang their lyres on the willows on the bank. Those who had carried them captive asked them for songs, with mirth, saying: sing us one of the songs of Zion. It was mockery, for they were asked to entertain their oppressors with the music of their faith.
Verse 4 asks the central question: how shall we sing the Lord's song in a foreign land? Verses 5 and 6 are an oath: if I forget you, O Jerusalem, let my right hand forget its skill, let my tongue stick to the roof of my mouth if I do not remember you, if I do not set Jerusalem above my highest joy. Memory is loyalty and faith.
Verses 7 to 9 are a harsh prayer. It asks the Lord to remember the sons of Edom, who on the day of Jerusalem cried out: tear it down to its foundations. It announces the destruction of the daughter of Babylon and calls blessed the one who repays her for what she did and who takes her little ones and dashes them against the rock. It is a cry for vengeance full of pain.