Psalm 137

“By rivers of Babylon, there we sat; also we wept when we remembered Zion. On willows in its midst we hung our harps; for there our captors asked us words of song, and our spoilers mirth, [saying] Sing to us from a song of Zion. How shall we sing the song of Jehovah on a strange ground? If I forget thee, Jerusalem, let my right hand forget [its skill]. Let my tongue cleave to my palate—if I do not raise Jerusalem above my chief joy. Remember, Jehovah, to Edom's sons the day of Jerusalem, who said, Raze, raze, down to its foundation. Daughter of Babylon, the desolated, happy he that rendereth to thee thy measure thou didst mete to us. Happy he that taketh and dasheth thy babes against the rock (crag)” (vers. 1-9).
Very different were Babylon and Edom, both the enemies of Zion, one to humble her for her sins, the other hating her for divine favor, alike to suffer before Zion's joy, who must sorrow till then and not sing.