“WHOEVER has been separated from the Church is yoked with an adulteress, is separated from the promises made to the Church. Nor shall he who leaves Christ’s Church arrive at Christ’s rewards. He is a stranger, he is sacrilegious, he is an enemy. Who has not the Church for mother can no longer have God for the father.”
~St. Cyprian (c. 200 – 258), bishop of Carthage: On the Unity of the Catholic Church, 10.