6 And so it is that often something is imperfectly revealed to the more learned, that their patient and humble charity, from which proceeds the greater fruit, may be proved, either in the way in which they preserve unity, when they hold different opinions on matters of comparative obscurity, or in the temper with which they receive the truth, when they learn that it has been declared to be contrary to what they thought. And of these two we have a manifestation in the blessed Cyprian of the one, viz., of the way in which he preserved unity with those from whom he differed in opinion.
For he says, "Judging no one nor depriving any one of the right of communion if he differ from us." And the other, viz., in what temper he could receive the truth when found to be different from what he thought it, though his letters are silent on the point, is yet proclaimed by his merits. If there is no letter extant to prove it, it is witnessed by his crown of martyrdom; if the Council of bishops declare it not, it is declared by the host of angels. For it is no small proof of a most peaceful soul, that he won the crown of martyrdom in that unity from which he would not separate, even though he differed from it.
For we are but men; and it is therefore a temptation incident to men that we should hold views at variance with the truth on any point. But to come through too great love for our own opinion, or through jealousy of our betters, even to the sacrilege of dividing the communion of the Church, and of founding heresy or schism, is a presumption worthy of the devil. But never in any point to entertain an opinion at variance with the truth is perfection found only in the angels. Since then we are men, yet forasmuch as in hope we are angels, whose equals we shall be in the resurrection, at any rate, so long as we are wanting in the perfection of angels, let us at least be without the presumption of the devil.
Accordingly the apostle says, "There has no temptation taken you but such as is common to man." It is therefore part of man's nature to be sometimes wrong. Wherefore he says in another place, "Let us therefore, as many as be perfect, be thus minded: and if in anything ye be otherwise minded, God shall reveal even this unto you." But to whom does He reveal it when it is His will (be it in this life or in the life to come), save to those who walk in the way of peace, and stray not aside into any schism?
Not to such as those who have not known the way of peace, or for some other cause have broken the bond of unity. And so, when the apostle said, "And if in anything ye be otherwise minded, God shall reveal even this unto you," lest they should think that besides the way of peace their own wrong views might be revealed to them, he immediately added, "Nevertheless, whereto we have already attained, let us walk by the same rule." And Cyprian, walking by this rule, by the most persistent tolerance, not simply by the shedding of his blood, but because it was shed in unity (for if he gave his body to be burned, and had not charity, it would profit him nothing), came by the confession of martyrdom to the light of the angels, and if not before, at least then, acknowledged the revelation of the truth on that point on which, while yet in error, he did not prefer the maintenance of a wrong opinion to the bond of unity.
Source: On Baptism, Against the Donatists (New Advent)