This exceptional work forms part of series of saints that Zurbarán painted during his lifetime following a particular and personal criterion. Portrayed in profile and richly dressed, like a lady from the high Sevillian society, the religious character is practically relegated to the almost imperceptible halo round her head, with the prevalence of the sumptuous appearance of fabrics and adornments marvellously executed. According to tradition, Saint Casilda was the daughter of a Moslem king; converted to Christianity, she was surprised by the jailers when she was taking some loaves of bread to the Christian prisoners, and they were miraculously changed into roses.
