St Casimir, Vilnius Cathedral, Lithuania [Wikipedia]
St Casimir (3 October 1458 - 4 March 1484), whose feast day is today, 4 March, is patron saint of Poland, of Lithuania and of the young.
He was noted for his great love for the poor and for his chastity. The biographical note in The CTS New Daily Missal says: His devotion to Our Lady was great; he was so fond of the twelfth-century hymn 'Daily, daily sing to Mary' that it is often attributed to him. The hymn - its Latin title is Omni die, dic Mariae - was written by St Bernard. You can find both the Latin and English lyrics on CatholicCulture.org. A note there says A copy of this hymn by Bernard of Cluny was found beneath the right temple of St Casimir's incorrupt body when his grave was opened.
The biographical note in the CTS New Daily Missal describes St Casimir as A shining example of faith, piety, humility, and chastity. A priest I met in Scotland last year kindly gave me a copy of the Missal and I can recommend it to anyone. It has the prayers and antiphons of all Masses in both English and Latin and the Scripture readings are from the Jerusalem Bible.
And here is a setting of the original Latin, Omni die, dic Mariae, sung, appropriately, by a Lithuanian choir, Schola Cantorum de Regina Pacis, Klaipėda, Lithuania.