"Non é Gran Causa" is one of the about 400 monophonic song (Cantigas) about the pilgrims of Santiago. The music, attributed to Alfonso X El Sabio, has been set as a
vocalise by Loreena McKennitt.
Let me copy-paste the story from
The Oxford Cantigas de Santa Maria database:
A man made an annual pilgrimage to Santiago de Compostela. One time, before setting off, he spent the night with a prostitute and left on his journey without confessing his sins.
The devil, appeared to him “whiter then ermine” / “mais branco que un armyo” in the guise of St James. He commanded him to cut off his penis and to slit his throat. The pilgrim did as he was told and was found dead by his companions. They ran away so they would not be accused of murdering him.
Demons came to carry away the pilgrim’s soul. As they were bearing it aloft, they passed a chapel dedicated to St Peter, and St James rushed out and accused them of winning the soul deceitfully. The demons protested that the pilgrim had committed evil deeds and committed suicide. St James suggested the Virgin settle the dispute over the soul.
Mary ordered the soul to be returned to the pilgrim’s body and he was revived. However, his member was not restored.
