From his epistle to the Smyrnaeans:
…They [Docetists, who believed Christ did not have true human body] even absent themselves from the Eucharist and the public prayers, because they will not admit that the Eucharist is the self-same body of our Saviour Jesus Christ which suffered for our sins….Abjure all factions, for they are the beginnings of evils. Follow your bishop, every one of you, as obediently as Jesus Christ followed the Father. Obey your clergy too, as you would the Apostles….
Bishop Ignatius of Antioch, obtaining his bishopric around AD 67, serving while some of the Apostles were still alive, himself tutored under the Apostle John in Ephesus, martyred in 107 AD.