When the emperor Leo the Armenian (813-820) renewed the persecution against Orthodox Christians because they venerated the holy icons, Saint Gregory of Decapolis and Saint Joseph the Hymnographer (April 4) and his disciple Saint John went from Thessalonica to Constantinople, to raise opposition to the Iconoclast heresy.
In spite of persecution, Saints Gregory and John fearlessly defended Orthodoxy for several years, and preached the veneration of icons. After many hardships Saint Gregory died (around 820), and soon after, his faithful disciple John also departed to the Lord. Saint Joseph the Hymnographer transferred the relics of Saints Gregory and John and placed them in the church of Saint Nicholas the Wonderworker.
Troparion — Tone 8
The image of God was truly preserved in you, O Father, / for you took up the Cross and followed Christ. / By so doing you taught us to disregard the flesh for it passes away / but to care instead for the soul, since it is immortal. / Therefore your spirit, venerable John, rejoices with the angels.
Kontakion — Tone 1
Blessed John, with the Lord’s Cross upon your shoulder, / you climbed to the summit of virtues. / In place of passing pleasures / you attained the glory of the Kingdom of Heaven.