Psalms 137:3 - Joseph Benson’s Commentary on the Old and New Testaments

There they that carried us away Our new masters, who had made us their slaves, and carried us captives out of our own land; required of us a song דברי שׁיר, the words of a song: in the LXX., λογους ωδων, words of songs. They required us to entertain them with our music and singing. And they that wasted us Hebrew, ותוללינו, contumulatores nostri, they that laid us on heaps, namely, that laid Jerusalem and the temple in ruins, required of us mirth, שׁמחה, joy, or gladness; saying, Sing us of the songs (so it is in the Hebrew) of Zion Sing us some of those songs which were wont to be sung in the temple on occasions of public joy. This they required, probably partly out of curiosity, and partly by way of scoffing and insult over them and their temple and worship, not without “a tacit reflection on their God, who could not protect his favoured people against their enemies. Thus the faithful have been, and thus they will be insulted over in the day of their calamity.”