St. Casimir was born in 1458, son of Casimir IV, king of Poland. Casimir was one of thirteen children. With the help of his virtuous mother and his dedicated teacher, Casimir received an excellent education.
When he was thirteen, Casimir had the chance to become king of neighboring Hungary, but he refused. He spent the rest of his life trying to live his Christian ideals. He went out of his way to be cheerful and friendly with everybody. Beneath the surface of his busy life, he made the effort to help himself to grow spiritually. He often fasted and slept on the floor of his room as penance. He prayed daily, sometimes even during the middle of the night. He loved to think and pray about the passion of Jesus. He recognized this as a good way to learn to love God. Casimir also loved the Blessed Virgin Mary with a special love. In her honor, he recited a beautiful hymn very often. The name of the hymn is "Daily, Daily, Sing to Mary." His hand-written copy of it was buried with him.
Casimir was never healthy, yet he was courageous and strong in character. He would always do what he knew was right. Sometimes he would even advise his father, the king, to rule the people fairly. He always did this with great respect and his father listened to him.
St. Casimir had a great love and respect for virginity. His parents found a very beautiful and virtuous young woman for him to marry. However, Casimir chose to give his heart to God alone. While in Lithuania on an assignment of service for that country, Casimir became ill with tuberculosis. He died at the age of twenty-six. He was proclaimed a saint by Pope Leo X in 1521.
Although Casimir didn't fulfill the expectations of those around him, he listened to God speaking in his life and lived his faith with courage.