Matthew Henry on Psalms 137

Their enemies had carried the Jews captive from their own land. To complete their woes, they insulted over them; they required of them mirth and a song. This was very barbarous; also profane, for no songs would serve but the songs of Zion. Scoffers are not to be compiled with. They do not say, How shall we sing, when we are so much in sorrow? but, It is the Lord's song, therefore we dare not sing it among idolaters.

What we love, we love to think of. Those that rejoice in God, for his sake make Jerusalem their joy. They stedfastly resolved to keep up this affection. When suffering, we should recollect with godly sorrow our forfeited mercies, and our sins by which we lost them. If temporal advantages ever render a profession, the worst calamity has befallen him. Far be it from us to avenge ourselves; we will leave it to Him who has said, Vengeance is mine. Those that are glad at calamities, especially at the calamities of Jerusalem, shall not go unpunished. We cannot pray for promised success to the church of God without looking to, though we do not utter a prayer for, the ruin of her enemies. But let us call to mind to whose grace and finished salvation alone it is, that we have any hopes of being brought home to the heavenly Jerusalem.