22 Faith in the Church cannot stand pure and true without the support of faith in the primacy of the Bishop of Rome. The same moment when Peter, in the presence of all the Apostles and disciples, confesses his faith in Christ, Son of the Living God, the answer he received in reward for his faith and his confession was the word that built the Church, the only Church of Christ, on the rock of Peter ( Matt . xvi. 18). Thus was sealed the connection between the faith in Christ, the Church and the Primacy. True and lawful authority is invariably a bond of unity, a source of strength, a guarantee against division and ruin, a pledge for the future: and this is verified in the deepest and sublimest sense, when that authority, as in the case of the Church, and the Church alone, is sealed by the promise and the guidance of the Holy Ghost and His irresistible support. Should men, who are not even united by faith in Christ, come and offer you the seduction of a national German Church, be convinced that it is nothing but a denial of the one Church of Christ and the evident betrayal of that universal evangelical mission, for which a world Church alone is qualified and competent. The live history of other national churches with their paralysis, their domestication and subjection to worldly powers, is sufficient evidence of the sterility to which is condemned every branch that is severed from the trunk of the living Church. Whoever counters these erroneous developments with an uncompromising No from the very outset, not only serves the purity of his faith in Christ, but also the welfare and the vitality of his own people.
Source: Mit Brennender Sorge (Vatican.va)