99 These last are recognizing in the Catholic Church principles of belief and life that have stood the test of 2,000 years; the strong cohesion of the Ecclesiastical Hierarchy, which in union with the Successor of Peter spends itself in enlightening minds with the teaching of the Gospel, in guiding and sanctifying men, and which is generous in its material condescension towards all, but firm when, even at the cost of torments or martyrdom, it has to say: "Non licet; it is not allowed!"
Source: Summi Pontificatus (Vatican.va)