57 But if the erring continue obstinately to scatter the seeds of dissension and error, to waste the patrimony of the sacred doctrine of the Church, to attack discipline, to heap contempt on venerated customs, "to destroy which is a species of heresy" in the phrase of St. Anselm, and to destroy the constitution of the Church in its very foundations, then all the more strictly must we watch, venerable brethren, and keep away from Our flock, and especially from youth which is the most tender part of it, so deadly a pest. This grace We implore of God with incessant prayers, interposing the most powerful patronage of the august Mother of God and the intercession of the blessed citizens of the Church triumphant, St. Anselm especially, shining light of Christian wisdom, incorrupt guardian and valiant defender of all the sacred rights of the Church, to whom We would here, in conclusion, address the same words that Our Holy Predecessor, Gregory VII, wrote to him during his lifetime: "Since the sweet odor of your good works has reached Us, We return due thanks for them to God, and We embrace you heartily in the love of Christ, holding it for certain that by your example the Church of God has been greatly benefited, and that by your prayers and those of men like you she may even be liberated from the dangers that hang over her, with the mercy of Christ to succor us" (S. Anselm, "De nuptiis consanguinerorum," cap. 1). "Hence We beg your fraternity to implore God assiduously to relieve the Church and Us who govern it, albeit unworthily, from the pressing assaults of the heretics, and lead these from their errors to the way of truth" (In lib . ii. Epist. S. Anselmi , ep. 31).
Source: Communium Rerum (Vatican.va)