Charles H. Spurgeon on Psalms 137:3

"They that carried us away captive required of us a song; " or rather, as it should be rendered, "the words of a song." They see no inconsistancy in a religion which freely mixes with the world. In their ignorance they only require "the words of a song; "its heavenly strain they have never caught. "They that wasted us" required of us mirth." Remember, it is this worldly element which wasteth, or lays on heaps, whether so far as our own hearts of the church of God is concerned. But, true to his spiritual instincts, the child of God replies, "How shall we sing Jehovah's song in the land of a stranger?" and then, so far from being utterly cast down or overcome, rises with fresh outburst or resolution and intenseness of new vigour, to utter the vows of verses 5 and 6. For, after having passed through such a spiritual conflict, we come forth, not wearied, but refreshed; not weaker, but stronger. It is one of the seeming contradictions of the gospel, that the cure of weariness, and the relief of heavy-ladenness, lies in this —to take the cross upon ourselves. After the night long conflict of Israel," as he passed over Peniel, the sun rose upon him, "and that though "he halted upon his thigh." —Alfred Edersheim.