They hang their harps on willow trees, refusing to play.
Their Babylonian captors mockingly ask them to sing "one of the songs of Zion" for entertainment.
The psalm begins with a haunting image of the Jewish exiles sitting by the waters of Babylon (the Tigris and Euphrates), weeping as they remember their homeland, Zion.
Verse 4 contains the famous rhetorical question: "How can we sing the Lord’s song in a foreign land?" . 2. A Vow of Remembrance