"He who hears you hears me, and he who rejects you, rejects me, and he who rejects me, rejects him who sent me (Lk 10:16).”
“If any man preaches any other Gospel unto you than that ye have received, let him be accursed” (Gal 1: 9).
“And we charge you, brethren, in the name of Our Lord Jesus Christ that you withdraw yourselves from every brother walking disorderly and not according to the Tradition which they have received of us” (2 Thess 3:6).
“If any man come to you and bring not this doctrine, receive him not into the house or welcome him” (2 Jo 1:10)”
“To be Christian one must be Roman. One must recognize the oneness of Christ’s Church that is governed by one successor of the Prince of the Apostles who is the Bishop of Rome, Christ’s Vicar on earth” - Pope Pius XII
"“So long as the member was on the body, it lived; separated, it lost its life. Thus the man, so long as he lives on the body of the [Catholic] Church, he is a Christian; separated from her, he becomes a heretic” - Leo XIII
“Whoever leaves her [the Catholic Church] departs from the will and command of Our Lord Jesus Christ; leaving the path of salvation, he enters that of perdition. Whoever is separated from the Church is united to an adulteress” - Leo XIII
“He who abandons the Chair of Peter on which the Church is founded, is falsely persuaded that he is in the Church of Christ” - Pius IX