Pope Pius XI, Divini Illius Magistri (#18), Dec. 31, 1929: “… God Himself made the Church a sharer in the divine magisterium and by His divine benefit unable to be mistaken.”
LATIN: “… divini magisterii Ecclesiam fecit Deus ipse participem eamdemque divino eius beneficio falli nesciam.”
Pope Pius XI, Divini Illius Magistri (#16), Dec. 31, 1929: “To this magisterium Christ the Lord imparted immunity from error...”
LATIN: “Huic magisterio Christus Dominus erroris immunitatem impertivit...”
Pope Gregory XVI, Commissum Divinitus (# 4), May 17, 1835: “... the Church has, by its divine institution, the power of the magisterium to teach and define matters of faith and morals and to interpret the Holy Scriptures without danger of error.”
Pope Leo XIII, Caritatis Studium (#6) July 25, 1898: The Magisterium “could by no means commit itself to erroneous teaching.”
Pope Pius X, Editae Saepe (#8), May 26, 1910: “... only a miracle of that divine power could preserve the Church... from blemish in the holiness of Her doctrine...”
Pope Pius XI, Quas Primas (#22), Dec. 11, 1925: “... the perfect and perpetual immunity of the Church from error and heresy.”
Pope Leo XIII, Satis Cognitum (# 9), June 29, 1896: “The practice of the Church has always been the same, and that with the consenting judgment [i.e. consensus] of the holy fathers who certainly were accustomed to hold as having no part of Catholic communion and as banished from the Church whoever had departed in even the least way from the doctrine proposed by the authentic magisterium.”
LATIN: "Idem semper Ecclesiae mos, idque sanctorum patrum consentiente iudicio: qui scilicet communionis catholicae expertem et ab Ecclesia extorrem habere consueverunt, quicuмque a doctrina authentico magisterio proposita vel minimum discessisset.”
Pope Gregory XVI, Mirari Vos (# 10), Aug. 15, 1832: “Therefore, it is obviously absurd and injurious to propose a certain ‘restoration and regeneration’ for her (the Church) as though necessary for her safety and growth, as if she could be considered subject to any failing health or dimming of mind or other misfortune.”
Pope Pius XI, Mortalium Animos (# 10), Jan. 6, 1928: “During the lapse of centuries, the mystical Spouse of Christ has never been contaminated, nor can she ever in the future be contaminated, as Cyprian bears witness: ‘The Bride of Christ cannot be made false to her Spouse: she is incorrupt and modest. She knows but one dwelling, she guards the sanctity of the nuptial chamber chastely and modestly.”
Pope Hadrian I, Second Council of Nicaea, 787: “… Christ our God, when He took for His Bride His Holy Catholic Church, having no blemish or wrinkle, promised he would guard her and assured his holy disciples saying, I am with you every day until the consummation of the world.”
Pope Eugene IV, Council of Florence, Session 9, March 23, 1440: “…the Spouse of Christ is uncontaminated and modest, knowing only one home, and she guards the sanctity of their marriage bed with chaste modesty.”
Pope St. Siricius, epistle (1) Directa ad decessorem, Feb. 10, 385: “And so He has wished the beauty of the Church, whose spouse He is, to radiate with the splendor of chastity, so that on the day of judgment, when He will have come again, He may be able to find her without spot or wrinkle [Eph. 5:27] as He instituted her through His apostle.”