Wallace Smith - On the Willows lyrics

On the willows, there We hung up our lives For our captors there Require Of us songs And our tormentors mirth On the willows, there We hung up our lives For our captors there Require Of us songs And our tormentor's mirth Saying Sing us one Of the songs of Sion Sing us one Of the songs of Sion But how can we sing? Sing the Lord's songs? In a foreign land?