A Prince of the Captivity by John Buchan

There followed a week of more bitter emptiness than he had ever known before. He had let his dreams run away with him, and had suddenly awoke to their baselessness. Eilean Bàn seemed to slip out of the world into some eternal ocean where Nigel, for ever out of his reach, played on its sands. He felt himself naked, stripped to the buff, without a rag to call his own.

Those were days of dull misery and nights of dreamless sleep and unrefreshed awakening. And then one morning he arose with a verse in his head. He had always been a voracious reader of poetry, and had remembered the things which caught his fancy. This verse was about the soul and body being ploughed under by God. He had forgotten the author, but bit by bit he managed to build up one quatrain, and it seemed to run something like this: