This divine Father, who was from Asia Minor, was from childhood reared in the royal court of Constantinople, where he was instructed in both religious and secular wisdom. Later, while still a youth, he left the imperial court and struggled in asceticism on Mount Athos, and in the Skete at Beroea. He spent some time in Thessalonica being treated for an illness that came from his harsh manner of life. He was present in Constantinople at the Council that was convened in 1341 against Barlaam of Calabria, and at the Council of 1347 against Acindynus, who was of like mind with Barlaam; Barlaam and Acindynus claimed that the grace of God is created. At both these Councils, the Saint contended courageously for the true dogmas of the Church of Christ, teaching in particular that divine grace is not created, but is the uncreated energies of God which are poured forth throughout creation: otherwise it would be impossible, if grace were created, for man to have genuine communion with the uncreated God. In 1347 he was appointed Metropolitan of Thessalonica. He tended his flock in an apostolic manner for some twelve years, and wrote many books and treatises on the most exalted doctrines of our Faith; and having lived for a total of sixty-three years, he reposed in the Lord in 1359.

His holy relics are kept in the Cathedral of Thessalonica. A full service was composed for his feast day by the Patriarch Philotheus in 1368, when it was established that his feast be celebrated on this day. Since works without right faith avail nothing, we set Orthodoxy of faith as the foundation of all that we accomplish during the Fast, by celebrating the Triumph of Orthodoxy the Sunday before, and the great defender of the teachings of the holy Fathers today.

Theophylact was from the East; his native city is unknown. In Constantinople he became a close friend of Tarsius, who afterwards became Patriarch of Constantinople (see Feb. 25).Theophylact was made Bishop of Nicomedia. After the death of Saint Tarsius, his successor Nicephorus (see June 2) called together a number of Bishops to help him in fighting the iconoclasm of Emperor Leo the Armenian, who reigned from 813-820. Among them was Euthymius, Bishop of Sardis (celebrated Dec. 26), who had attended the holy Seventh Ecumenical Council in 787 - he was exiled three times for the sake of the holy icons, and for defying the Emperor Theophilus' command to renounce the veneration of the icons, was scourged from head to foot until his whole body was one great wound, from which he died eight days later, about the year 830; Joseph of Thessalonica (see July 14); Michael of Synnada (see May 23); Emilian, Bishop of Cyzicus (see Aug. 8); and Saint Theophylact, who boldly rebuked Leo to his face, telling him that because he despised the long-suffering of God, utter destruction was about to overtake him, and there would be none to deliver him. For this, Theophylact was exiled to the fortress of Strobilus in Karia of Asia Minor, where, after 30 years of imprisonment and hardship, he gave up his holy soul about the year 845. Leo the Armenian, according to the Saint's prophecy, was slain in church on the eve of our Lord's Nativity, in 820.