The Marian hymn “found” in St. Casimir’s tomb

In 1604, Church officials opened the tomb of Saint Casimir in the cathedral of Vilnius during the solemn translation of his relics. The young royal, who had died more than a century earlier, was already venerated across Poland and Lithuania for a life of unusual holiness. According to longstanding Catholic tradition recorded in early accounts of the event, witnesses said a copy of the Latin Marian hymn Omni die dic Mariae — “Daily, daily sing to Mary” — was found in his coffin.

Historians treat the detail cautiously, as a devotional tradition rather than a fully documented discovery, but the story reflects something well established about Casimir’s life: his deep and constant devotion to the Virgin Mary.

Casimir was born in 1458 into the powerful Jagiellonian dynasty, which ruled a vast realm stretching across Central and Eastern Europe. His father, Casimir IV Jagiellon, governed a kingdom that stood at the crossroads of Latin and Eastern Christianity, trade routes, and political tensions. From an early age the young prince was educated for statecraft and diplomacy. As a teenager he was even sent to lead a political campaign in Hungary during a contested succession. Yet the prince who returned to Kraków became known less for ambition than for personal austerity, charity to the poor, and a striking seriousness about the spiritual life.

Contemporary sources describe Casimir praying late into the night in cathedral chapels and refusing the luxuries expected of a royal heir. His devotion to Mary was central to this discipline. He cultivated the habit of addressing her daily in prayer, a practice that later tradition linked to the hymn Omni die dic Mariae.

The prince died in 1484 at the age of 25, most likely from tuberculosis, after a prolonged illness endured with patience. His reputation for sanctity spread quickly, and he was canonized in 1521 by Pope Leo X. Today he is honored as a patron saint of both Poland and Lithuania.

The hymn associated with him, however, is far older. Omni die dic Mariae is generally attributed to Bernard of Cluny, one of the most important Latin poets of the Middle Ages. Bernard is best known for his sweeping satirical and devotional poem De Contemptu Mundi, a monumental critique of the moral corruption of medieval society that also produced the famous lines later adapted into the hymn “Jerusalem the Golden.” His Marian poetry shares the same vivid imagery and theological depth.

In Omni die dic Mariae, the poet invites the soul to praise Mary as advocate, mother, and guide toward Christ, weaving together biblical imagery and centuries of Christian devotion.

The opening lines establish the rhythm of daily prayer:

The hymn unfolds as both praise and petition. Mary is invoked as “Seat of wisdom,” “Gate of heaven,” and the luminous “Morning star upon the sea,” titles that echo the Church’s long meditation on her role in salvation history. The final verses ask her to guard believers from pride, anger, and temptation, and to lead them safely toward eternal life.

Because tradition links the hymn so closely with Casimir’s personal devotion, it eventually became known in many places as the Prayer of St. Casimir, despite its earlier medieval origin. The association helped preserve the text in Central and Eastern European devotional culture and inspired later musical settings, including one by the Polish Baroque composer Grzegorz Gerwazy Gorczycki.

For Catholics in Poland and Lithuania, the story of the hymn in Casimir’s tomb endures as a symbol of the saint’s interior life: A prince raised amid political power chose instead a discipline of prayer, charity, and Marian devotion. Whether the hymn truly rested in his coffin or not, the tradition expresses a truth about the young royal whose memory still inspires the Church: praise offered daily becomes a path toward holiness.