to Lithuania to be with his ill son. Prince Casimir died on 4 March 1484, in Grodno. His remains were interred in Vilnius Cathedral, where the dedicated Saint Casimir's Chapel was built in 1636. Veneration Pious life and attributed miracles Surviving contemporary accounts described Prince Casimir as a young man of exceptional intellect and education, humility and politeness, who strove for justice and fairness. Early sources do not attest to his piety or devotion to God, but his inclination to religious life increased towards the end of his life. Later sources provide some stories of Casimir's religious life. Marcin Kromer (1512–1589) claimed that Casimir refused his physician's advice to have sexual relations with women in hopes to cure his illness. Other accounts claimed that Casimir contracted his lung disease after a particularly hard fast or that he could be found pre-dawn, kneeling by the church gates, waiting for a priest to open them. Zacharias Ferreri (1479–1524) wrote that Casimir composed a prayer in hexameter on Christ's incarnation but this text has not survived. Later, a copy of Omni die dic Mariae (Daily, Daily Sing to Mary) was found in Casimir's coffin. The hymn became so strongly associated with Casimir that sometimes it known as Hymn of St. Casimir and he is credited as its author. The lengthy hymn has an intricate meter and rhyme scheme (alternate acatalectic and catalectic trochaic dimeter with internal rhyme in the first and third verses (aa/b, cc/b)) and was most likely written by Bernard of Cluny. One of the first miracles attributed to Casimir was his appearance before the Lithuanian army during the Siege of Polotsk in 1518. Casimir showed where Lithuanian troops could safely cross the Daugava River and relieve the city, besieged by the army of the Grand Duchy of Moscow. Ferreri's hagiography of 1521 mentions many miracles of Casimir are known but describes only one – a Lithuanian victory against the Russians. The description lacks specifics, such as date or location, but most likely refers to the Lithuanian victory in 1519 against Russian troops that raided environs of Vilnius, and not the more popular story of the Siege of Polotsk. Canonization and official veneration Casimir's official cult started spreading soon after his death. Already in 1501, Pope Alexander VI, citing chapel's splendor and Casimir's miracles, granted a special indulgence to those who would pray in the chapel where Casimir was buried from