13 Hence it is in vain that some who are overcome by reason oppose to us custom, as if custom were greater than truth; or as if that were not to be sought after in spiritual matters which has been revealed as the better by the Holy Spirit. For one who errs by simplicity may be pardoned, as the blessed Apostle Paul says of himself, “I who at first was a blasphemer, and a persecutor, and injurious; yet obtained mercy, because I did it ignorantly.” But after inspiration and revelation made to him, he who intelligently and knowingly perseveres in that course in which he had erred, sins without pardon for his ignorance. For he resists with a certain presumption and obstinacy, when he is overcome by reason. Nor let any one say, “We follow that which we have received from the apostles,” when the apostles only delivered one Church, and one baptism, which is not ordained except in the same Church. And we cannot find that any one, when he had been baptized by heretics, was received by the apostles in the same baptism, and communicated in such a way as that the apostles should appear to have approved the baptism of heretics.
Source: The Epistles of Cyprian (New Advent)