On Sunday, the Diocese of Winona-Rochester celebrated the feast day of St. Leander of Seville, a 6th-century bishop.

"Today we celebrate the feast of St. Leander of Seville, a bishop in Seville, Spain, who was later exiled to Constantinople," a diocese Facebook post said Monday. "He became close friends with St. Gregory the Great during his time in exile. St. Leander of Seville, pray for us!" 

St. Leander of Seville lived in the 6th century, a report on catholic.org said. He dedicated much of his life to combatting heresy within the Church and is credited with introducing the Nicene Creed that Catholics recite during Mass. 

Leander's feast day is celebrated every March 13, a recent release on FranciscanMedia.org said. 

The Spanish Church honors Leander as a "Doctor of the Church," an official title that a pope can bestow upon a person who has made significant and lasting contributions to the church. 

Throughout the history of the Catholic Church, only 36 people have been granted this title, a report on CrossroadsInitiative.com said. The three requirements to becoming a Doctor of the Church are: "holiness that is truly outstanding, even among saints; depth of doctrinal insight; and an extensive body of writings which the church can recommend as an expression of the authentic and life-giving Catholic Tradition."