11 For in fact, as to what some opposed to the reasoning of Cyprian, that the apostle says, "Notwithstanding every way, whether in pretence or in truth, let Christ be preached;" Cyprian rightly exposed their error, showing that it has nothing to do with the case of heretics, since the apostle was speaking of those who were acting within the Church, with malicious envy seeking their own profit. They announced Christ, indeed, according to the truth whereby we believe in Christ, but not in the spirit in which He was announced by the good evangelists to the sons of the dove.
"For Paul," he says, "in his epistle was not speaking of heretics, or of their baptism, so that it could be shown that he had laid down anything concerning this matter. He was speaking of brethren, whether as walking disorderly and contrary to the discipline of the Church, or as keeping the discipline of the Church in the fear of God. And he declared that some of them spoke the word of God steadfastly and fearlessly, but that some were acting in envy and strife; that some had kept themselves encompassed with kindly Christian love, but that others entertained malice and strife: but yet that he patiently endured all things, with the view that, whether in truth or in pretence, the name of Christ, which Paul preached, might come to the knowledge of the greatest number, and that the sowing of the word, which was as yet a new and unaccustomed work, might spread more widely by the preaching of those that spoke.
Furthermore, it is one thing for those who are within the Church to speak in the name of Christ, another thing for those who are without, acting against the Church, to baptize in the name of Christ." These words of Cyprian seem to warn us that we must distinguish between those who are bad outside, and those who are bad within the Church. And those whom he says that the apostle represents as preaching the gospel impurely and of envy, he says truly were within. This much, however, I think I may say without rashness, if no one outside can have anything which is of Christ, neither can any one within have anything which is of the devil.
For if that closed garden can contain the thorns of the devil, why cannot the fountain of Christ equally flow beyond the garden's bounds? But if it cannot contain them, whence, even in the time of the Apostle Paul himself, did there arise among those who were within so great an evil of envy and malicious strife? For these are the words of Cyprian. Can it be that envy and malicious strife are a small evil? How then were those in unity who were not at peace? For it is not my voice, nor that of any man, but of the Lord Himself; nor did the sound go forth from men, but from angels, at the birth of Christ, "Glory to God in the highest, and on earth peace to men of good will." And this certainly would not have been proclaimed by the voice of angels when Christ was born upon the earth, unless God wished this to be understood, that those are in the unity of the body of Christ who are united in the peace of Christ, and those are in the peace of Christ who are of good will.
Furthermore, as good will is shown in kindliness, so is bad will shown in malice.
Source: On Baptism, Against the Donatists (New Advent)