Charles H. Spurgeon on Psalms 137:5

If I forget thee, O Jerusalem, let my right hand forget her cunning. To sing Zion's songs for the pleasure of Zion's foes, would be to forget the Holy City Each Jew declares for himself that he will not do this; for the pronoun alters from "we" to "I." Individually the captives pledge themselves to fidelity to Jerusalem, and each one asserts that he had sooner forget the art which drew music from his harp strings than use it for Babel's delectation. Better far that the right hand should forget its usual handicraft, and lose all its dexterity, than that it should fetch music for rebels out of the Lord's instruments, or accompany with sweet skill a holy Psalm desecrated into a common song for fools to laugh at. Not one of them will thus dishonour Jehovah to glorify Belus and gratify his vetaries. Solemnly they imprecate vengeance upon themselves should they so false, so faithless prove.