St. Casimir known to the people of Poland as "The Peace-maker," was the third of the thirteen children of Casimir IV, King of Poland. Casimir was devout from the time he was a little child, and was known for his life dedicated to prayer and penance. Although he was part of the royal family, he often made his bed on the ground, and he would spend lots of the night in prayer and meditation, especially on the passion of Christ. He always wore very plain clothing, and under them he wore a hairshirt.
Because he lived constantly in the presence of God, Casimir always seemed serene and cheerful, and pleasant to everybody. He had a tremendous love of the poor, whom he saw as members of Christ's body, and he was known for giving his possessions away to relive the suffering of the poor.
Throughout his life he had a great devotion to the Blessed Virgin Mary, and he would often recite a long and beautiful hymn to the Virgin Mother – a hymn we know in English as "Daily, daily sing to Mary."
There came the time when the noblemen of neighboring Hungary became dissatisfied with their king. In 1471 they went to King Casimir of Poland, the father of St. Casimir, to allow them to place young Casimir on the throne. At that time, Casimir hadn’t yet turned fifteen years old, and he really wanted no part of the plan, but in obedience to his father he set out towards Hungary at the head of an army.
As they got closer, Casimir’s soldiers heard that the King of Hungary had assembled a large and strong army, and so Casimir’s army began to desert and go back home. Casimir had been given no money by his father or the Hungarian noblemen, so he wasn’t able to pay his soldiers to stay. It became obvious that Casimir wasn’t going to be able to march into Hungary with any kind of an army at all, so on the advice of his officers, he decided to return home to Poland.
King Casimir was very angry with his son Casimir. He had wanted to see his son on the throne of Hungary, because that meant he could control that country, as well as be King of Poland. As young Casimir got closer to home, his father had troops meet him, and instead of allowing the young boy to go to his family in Cracow, his father imprisoned him in a dark, musty castle.
Young Casimir accepted that with great patience, and let his father know that he would stay in the castle dungeon forever, before he would ever take up arms again. His father finally released him, and Casimir returned to his life of study and prayer, but his life of penance and his time in the dungeon, meant that he developed a disease of the lungs, and he died when he was only twenty-six years old. He was buried at the Church of St. Stanislaus in Vilna. Many miracles were reported at his tomb, and he was canonized in 1521.
O God, who, amidst the pleasures of a temporal kingdom, didst endue thy blessed Saint Casimir with constancy to resist all temptations: grant, we beseech thee; that by his intercession, thy faithful people may learn to despise all things earthly, and to seek earnestly after all things heavenly; through Jesus Christ thy Son our Lord, who liveth and reigneth with thee, in the unity of the Holy Spirit, ever one God, world without end. Amen.