Saint Gennady, Patriarch of Tsaregrad, was placed on the throne of the Church of Constantinople in 458, during the reign of the holy King Leo the Great (457-474). We know about his life from the book "The Spiritual Meadow," where the stories of the monks of the monastery of Salama (near Alexandria), St. Sophronius and John, were recorded. These monks were clerics of the Church of Constantinople under Patriarch Gennady. Saint Gennady was distinguished by his meekness, patience, purity, and abstinence. The power of his prayer can be judged from the following case: in the church of the Holy Martyr Eleutherius in Constantinople, there was an unworthy cleric, Harisim, who spent his life in laziness, uncleanness, and even engaged in robbery and magic. Saint Gennady exhorted him for a long time with meekness and patience, but Harisim did not change his behavior. The patriarch resorted to severity and ordered to give the unworthy cleric a few blows to bring him to reason. But even after the punishment, he did not improve. 
Then Saint Gennady instructed his envoy to address on his behalf the Holy Martyr Eleutherius (August 4), in whose church Harisim served. Arriving at the temple, the patriarch's envoy stood in front of the altar, stretched out his hand to the tomb of the martyr and said: "Holy Martyr Eleutherius! Patriarch Gennady announces to you through me, a sinner, that the cleric Harisim, who serves in your church, commits many iniquities and creates temptations; therefore, you either correct him or cut him off from the Church." The next morning, Harisim was found dead. Another case testifying to the great power of St. Gennady's prayer occurred with a painter who dared to paint the image of Christ, giving the Savior the features of the pagan deity Zeus. The painter's hand, which had committed such sacrilege, immediately withered. The painter repented in the church, confessing his sin to the patriarch. Saint Gennady prayed for the sinner, and the painter's hand was healed.
To eliminate the illegal actions and false teachings that had arisen in the Church, St. Gennady convened a Local Council, at which the heresy of Eutychius was condemned and simony (ordination for a bribe) was prohibited. The saint made sure that those who wished to take holy orders were well acquainted with the Holy Scriptures and knew the Psalter by heart.
During the patriarchate of St. Gennady, a church was built in Constantinople in honor of St. John the Baptist. At the same time, a certain senator Studius, who came from Rome, founded a monastery, which later became known as the "Studium". The church steward under the Holy Patriarch Gennady was the Monk Marcian (commemorated on January 10). The saint ordained the Monk Daniel Stylites to the priesthood (commemorated on December 11). Saint Gennady was the author of discourses and interpretations on the prophet Daniel (the writings have not reached us). His "District Epistle against Simony," approved by the Council of 459, is well known. Saint Gennady ruled the Church of Constantinople for 13 years. He died peacefully in 471.
One day, during night prayer, the saint was informed that after his death, his flock would be heavily attacked by the enemy. He incessantly offered prayers for the peace of the Church, so that the Lord would keep it invincible by the gates of hell.