The painting of St Casilda follows a typology invented by Zurbaran and repeated in other paintings of martyr saints. The saint is represented full-length in half profile, with the appearance and rich clothing of a young woman of the 17th century. She is shown taking part in a procession, set against a dark background. St Casilda is associated with the miraculous transformation of bread into roses as was St Elizabeth of Hungary and Thuringia. Casilda was the daughter of the Emir of Toledo and was secretly converted to Christianity. She gave bread to her father's prisoners. When the bread was miraculously turned into flowers she was saved from exposure like the charitable Elizabeth who gave food to the poor.