7 But, moreover, you have well answered that part where Stephen said in his letter that heretics themselves also are of one mind in respect of baptism; and that they do not baptize such as come to them from one another, but only communicate with them; as if we also ought to do this. In which place, although you have already proved that it is sufficiently ridiculous for any one to follow those that are in error, yet we add this moreover, over and above, that it is not wonderful for heretics to act thus, who, although in some lesser matters they differ, yet in that which is greatest they hold one and the same agreement to blaspheme the Creator, figuring for themselves certain dreams and phantasms of an unknown God.
Assuredly it is but natural that these should agree in having a baptism which is unreal, in the same way as they agree in repudiating the truth of the divinity. Of whom, since it is tedious to reply to their several statements, either wicked or foolish, it is sufficient shortly to say in sum, that they who do not hold the true Lord the Father cannot hold the truth either of the Son or of the Holy Spirit; according to which also they who are called Cataphrygians, and endeavour to claim to themselves new prophecies, can have neither the Father, nor the Son, nor the Holy Spirit, of whom, if we ask what Christ they announce, they will reply that they preach Him who sent the Spirit that speaks by Montanus and Prisca.
And in these, when we observe that there has been not the spirit of truth, but of error, we know that they who maintain their false prophesying against the faith of Christ cannot have Christ. Moreover, all other heretics, if they have separated themselves from the Church of God, can have nothing of power or of grace, since all power and grace are established in the Church where the elders preside, who possess the power both of baptizing, and of imposition of hands, and of ordaining.
For as a heretic may not lawfully ordain nor lay on hands, so neither may he baptize, nor do any thing holily or spiritually, since he is an alien from spiritual and deifying sanctity. All which we some time back confirmed in Iconium, which is a place in Phrygia, when we were assembled together with those who had gathered from Galatia and Cilicia, and other neighbouring countries, as to be held and firmly vindicated against heretics, when there was some doubt in certain minds concerning that matter.
Source: The Epistles of Cyprian (New Advent)