On Sunday, the Diocese of Brooklyn celebrated the feast day of St. Leander of Seville, a 6th-century bishop, praising his dedication to building faith among the people.

"St. Leander of Seville was a Catholic bishop surrounded by Arians for much of his life," a diocese Facebook post said this week. "He fought hard to restore faith in the divinity of Christ, using the profession of the Nicene Creed as a tool." 

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

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

Leander is one of a select group of people who have earned the title of "Doctor of the Church," a report on CrossroadsInitiative.com said. That is an official title the pope has the authority to bestow upon a person who has made significant and long-term contributions to the Church. Throughout the long history of the Catholic Church, only 36 people have been granted this title. 

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," the Crossroads Initiative report said.