How inseperable the sacrament of unity is, and how without hope they are, and what exceeding perdition they purchase to themselves from the wrath of God, who make a schism, and abandoning their bishop set up for themselves another false bishop from without.
Holy Scripture declares in the Book of Kings, how ten tribes severed from the tribe of Judah and Benjamin, and abandoning their king, set up another for themselves without (1 Kings 12:17). "The Lord," it says, "was very angry with all the seed of Israel, and removed them away, and delivered them into the hand of spoilers, until He had cast them out of His sight; for Israel was rent from the house of David, and they made themselves a king, Jeroboam the son of Nebat." (2 Kings 17:20-21)
It is said that "the Lord was very angry," and gave them up to perdition, because they were seperated from unity, and had set up for themselves another king. And so great was the anger of the Lord against those who had caused the schism, that even when the man of God was sent to Jeroboam to reproach him for his sins, and to foretell the vengeance that would follow, he was forbidden "to eat bread or drink water" with them; which when he did not observe, and against the command of God took food (1 Kings 13:19), he was immediately stricken by the majesty of the Divine judgement, so that returning thence he was slain in the way by the jaws of a lion who came against him (1 Kings 13:24).
And does any one dare to say that the saving water of Baptism and heavenly grace can be in common with schismatics, with whom neither earthly food nor this world's drink ought to be in common?
~St. Cyprian of Carthage (3rd Century), Epistle 69