Pope St. Felix I

“As it took up in the beginning the norm of the Christian Faith from its authors, the Princes of the Apostles of Christ, She remains unsullied according to what the Lord said: ‘I have prayed for thee, etc.’ [Lk 22:32]” (quoted by Saint Robert Bellarmine. On the Roman Pontiff, vol. 2: Books III-V, De Controversiis, p. 157-158, Mediatrix Press [Pope from A.D. 269-274])