When Sixtus III became pope, St. Leo was sent to Gaul to settle an argument between the military commander, Aetius and the magistrate, Albinus.
St. Leo succeeded Pope Sixtus III and consecrated as pope on September 29, 440. He remained in the papacy for twenty years.
St. Leo was named a Doctor of the Church by Pope Benedict XIV in 1754.
St. Leo Worked for Church Unity
The main goal of St. Leo was to keep the Church unified. He fought against the heresies that threatened the Church. He assembled a provincial synod in Aquileia where he demanded that priests, deacons, and clerics deny Pelagianism in public and to abide by the confession of Faith.
St. Leo also fought against the secret meetings of Manichaeism. Eventually, many practitioners of Manichaeism were converted while the remainder was banished from Rome.
St. Leo threatened to excommunicate anyone who practiced any type of heresy, including bishops, pastors, or other clergy.
Pope St. Leo’s Sermons Preserved
Pope St. Leo was very active in preaching to the Roman congregation. His ninety-six sermons were preserved and are still studied. They reveal clear diction, profundity, and an educated style. The first five sermons are read on the anniversary of his consecration as pope. They depict the dignity of the papacy.