7 “Those” then “who have led us captive,” the devil and his angels, when have they spoken unto us: “Sing us one of the songs of Sion”? What answer we? Babylon bears you, Babylon contains you, Babylon nourishes you, Babylon speaks by your mouth, you know not to take in save what glitters for the present, you know not how to meditate on things of eternity, you take not in what you ask. “How shall we sing the Lord's song in a strange land?”. Truly, brethren, so it is. Begin to wish to preach the truth in such measure as you know it, and see how needful it is for you to endure such mockers, persecutors of the truth, full of falsehood. Reply to them, when they ask of you what they cannot take in, and say in full confidence of your holy song, “How shall we sing the Lord's song in a strange land!”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)