Casimir grew up in a world where his life was not his own. As a prince of Poland, the second son of King Casimir IV and Elizabeth of Austria, his life was scheduled to cement his father’s authority and increase Poland’s power.
Casimir realized from an early age that his life belonged to someone else, but to a much higher King than his father. Despite pressure, humiliation, and rejection, he stood by that loyalty through his whole life.

It may be hard for us to imagine royal luxury as a pressure. But for Casimir, the riches around him were temptations to forget his true loyalties. Rebelling against the rich, fashionable clothes he was expected to enjoy, he wore the plainest of clothes. Rejecting even ordinary comforts, he slept little, spending his nights in prayer. And when he did sleep, he lay on the floor not on a royal bed. Even though he was a prince, many of those around him must have laughed and joked at his choices. Yet, in the face of any pressure, Casimir was always friendly and calm.

He died at the age of 23 in 1484 from lung disease. He was buried with his favorite song, a Latin hymn to Mary called “Omni die dic Mariae” which we know as “Daily, Daily Sing to Mary.” Because of his love for the song, it is known as the Hymn of St. Casimir though he didn’t write it. Casimir is patron saint of Poland and Lithuania.