St. John Cassian

“That great man, the disciple of disciples, that master among masters, who wielding the government of the Roman Church possessed the principle authority in faith and in priesthood. Tell us, therefore, we beg of you, Peter, prince of Apostles, tell us how the Churches must believe in God.” (Cassian, Contra Nestorium, III, 12, CSEL, vol. 17, p. 276 [c. A.D. 430]).