St. Leander of Sevilla (524-600 AD) was instrumental in instituting the recitation of the Nicean Creed during the Mass. Leander sought to combat confusion over the heresy of Arianism, which balked at the 324 AD Council of Nicea declaration that that God the Father was one in being with the Second Person of the Holy Trinity Jesus. This practice of clearly professing the tenants of faith in the Nicean creed spread from Spain to throughout the Universal Church.
St. Leander came from a very devout Catholic family, like all of his siblings, in present day Cartegena, Spain. Leander first became a Benedictine monk and later was named the Bishop of Sevilla in 578. Leander's brothers St. Isadore and St. Fulgentius followed him as bishops of Sevilla. Leander's sister St. Florentina was a Abbess oversaw 40 convents and 1,000 nuns.
St. Leander presided over the third Council of Toledo in 589 which decreed the consubstantiality of the Holy Trinity. Leander also created an important rule for nuns on prayer and the renunciation of the world.
St. Leander's influence was much broader than the Iberian peninsula.by engendering the ire of a local king. To further combat Arianism amongst the Germanic rules in Iberia at the time. By praying to God through the mediation of Our Lady, Leander sought graces in his apostolate. His selfless prayers were answered and Leander achieved colossal conversions of Arian Christians, including Visogoth king's son.
King Leovigild was enraged at these attacks and killed his own son while exiling Leander to Constantinople. It was there that Leander become close friends of the Papal Legate, the future Pope Gregory V, who he encouraged to write Moralia, a famous commentary on the Book of Job.
|[L] Pope Gregory V presenting St. Leander with Moralia|
In Spain, St. Leander is considered to be a Doctor of the Church.