Ignatius of Antioch
Ignatius is generally considered to be one of the Apostolic Fathers (the earliest authoritative group of the Church Fathers) and a saint by the Roman Catholic Church, Lutheran Church, Eastern Orthodox Church and Anglican/Episcopal Church who celebrate his feast day on October 17, and the Orthodox and Eastern Catholic churches, who celebrate his feast day on December 20.  Ignatius based his authority on living his life in imitation of Christ.