In 815, emperor Leo V the Armenian [[deposition|deposed]] [[Patriarch]] [[Nicephorus I of Constantinople|Nikephoros]] as Patriarch of Constantinople, convened a [[synod]] at Constantinople, and re-instituted the second period of iconoclasm. As Gregory renewed his fight against the iconoclasts, he was overcome with illness that undermined his strength and resulted in his repose in 816.

At first, St. Gregory's body was buried at a [[monastery]] in Constantinople. His tomb was much visited and soon many [[miracle]]s occurred. Seeing this, the monks translated his [[relics]] to a shrine in the [[church]] to enable the people to venerate them more easily. After Constantinople was taken by the Ottoman Turks in 1453, a Turkish official moved his relics again, this time to a region near the Danube River. In 1498, hearing of the miracles performed through St. Gregory's relics, Barbu Craiovescu, the Ban of Wallachia, purchase them. Then, Barbu moved St. Gregory's relics to the main church of Bistritsa Monastery where they are today.