Saint Peter Damian, O.S.B. (Petrus Damiani, also Pietro Damiani or Pier Damiani; c. 1007 – February 21/22, 1072/1073) was a reforming monk in the circle of Pope Gregory VII and a cardinal. In 1823, he was declared a Doctor of the Church. Dante placed him in one of the highest circles of Paradiso as a great predecessor of Saint Francis of Assisi.
- Any cleric or monk who seduces young men or boys, or who is apprehended in kissing or in any shameful situation, shall be publicly flogged and shall lose his clerical tonsure. Thus shorn, he shall be disgraced by spitting in his face, bound in iron chains, wasted by six months of close confinement, and for three days each week put on barley bread given him toward evening. Following this period, he shall spend a further six months living in a small segregated courtyard in custody of a spiritual elder, kept busy with manual labor and prayer, subjected to vigils and prayers, forced to walk at all times in the company of two spiritual brothers, never again allowed to associate with young men.
- Let that ancient dragon, Cadalus, take note. Let this disturber of the Church, this destroyer of apostolic discipline, this enemy of man’s salvation understand. Let him beware, I say, this root of all sin, this herald of the devil, this apostle of Antichrist. And what else shall I call him? He is the arrow drawn from the quiver of Satan, the rod of the Assyrian, the son Belial, "the son of perdition, who rises in his pride against every god, so called, ever object of men’s worship" (2 Thess. 2:3-4), the whirlpool of lust, the shipwreck of chastity, the disgrace of Christianity, the ignominy of bishops, the progeny of vipers, the stench or the world, the filth of the ages, the shame of the universe. Still more epithets for Cadalus can be added, a list of darksome names: slippery snake, a twisting serpent, the dung of humanity, the latrine of crime, the dregs of vice, the abomination of heaven the expulsion from paradise, the fodder of hell, the stubble of eternal fire.
- Letter 120:13. Damian to young King Henry IV, A. D. 1065 or 1066, wherein Damian exhorts Henry to use his sword against the disturber of the Church’s peace, Cadalus, the bishop of Parma, the antipope Honorius II (d. 1072):
- The Fathers of the Church, Medieval Continuation, 1998, Letters 91-120, Owen J. Blum, Irven Michael Resnick, trs., Catholic University of America Press, ISBN 0813208165 ISBN 9780813208169, vol. 5, pp. 393-394. 
- But now, coming to your shameless assertion that ministers of the altar should be allowed to marry, I consider it superfluous to unsheathe the sword of my own words against you, since we see the armed forces of the whole Church and the massed array of all the holy Fathers ready to resist you. And where so great a host of heavenly troops opposes you, one can only wonder that your novel and rash attempt at doctrine does not submit when confronted by such authority.
- But you, my lord and venerable pope, you who take the place of Christ, and the successor to the supreme shepherd in apostolic dignity, do not through sloth allow this pestilence to grow, do not by conniving and dissimulation loosen the reins on this raging impurity. This disease is spreading like a cancer, and its poisonous breed will reach out endlessly unless its evil growth is cut off by the scythe of the gospel.
- Letter 61:14. To Pope Nicholas II. Damian “deplores the situation in which bishops live in public concubinage to the scandal of some, and to the delight of others who ridicule the leadership of the Church on this account.” January - July 1059.
- The Fathers of the Church, Medieval Continuation, Letters 61-90, 1992, Owen J. Blum, tr., Catholic University of America Press, ISBN 0813207509 ISBN 978-0813207506, vol. 3, p. 12 
- But if I have erred in anything, I gladly come before the teaching authority of Peter.
- Letter 65:26. To Hildebrand, "archdeacon and immobile pillar of the Apostolic See," Dec. 1059. Op. Cit., p. 39. 
- Sanctum Satanum meum.
- My holy Satan.
- Of Pope Gregory VII, in a letter (c. 1070) to Pope Alexander II and Cardinal Archdeacon Hildebrand, Ep. 1. I. ep. 16. T. I. f. 16.