Psalm 137 is A song of lament, oath, & oracle.  This is a Psalm acknowledging situations where it is excruciating to sing. The psalmist is in exile but his heart is in Zion.  This is a song Nehemiah could sing as he wept in the courts of Artaxerxes’ Persian controlled Babylon.  Nehemiah was a respected official who had the ear and the favor of an emperor, yet his affections called Jerusalem home (Neh 1:3-9). Nehemiah’s contentment was tied to the fortunes of Zion: the status of covenant relations between God & God’s people.  In his anguish our author lifts his appeal to The Great Judge of the nations.  The refrain spares no weight as the Psalmist finds consolation in the comprehensive judgements of a Holy God.