27 Neither let the new heretics flatter themselves in this, that they say that they do not communicate with idolaters; although among them there are both adulterers and fraudulent persons, who are held guilty of the crime of idolatry, according to the saying of the apostle: “For know this with understanding, that no whoremonger, nor unclean person, nor covetous man, whose guilt is that of idolatry, has any inheritance in the kingdom of Christ and of God.” And again: “Mortify therefore your members which are upon the earth; putting off fornication, uncleanness, and evil concupiscence, and covetousness, which are the service of idols: for which things' sake comes the wrath of God.” For as our bodies are members of Christ, and we are each a temple of God, whosoever violates the temple of God by adultery, violates God; and he who, in committing sins, does the will of the devil, serves demons and idols.
For evil deeds do not come from the Holy Spirit, but from the prompting of the adversary, and lusts born of the unclean spirit constrain men to act against God and to obey the devil. Thus it happens that if they say that one is polluted by another's sin, and if they con tend, by their own asseveration, that the idolatry of the delinquent passes over to one who is not guilty according to their own word; they cannot be excused from the crime of idolatry, since from the apostolic proof it is evident that the adulterers and defrauders with whom they communicate are idolaters.
But with us, according to our faith and the given rule of divine preaching, agrees the principle of truth, that every one is himself held fast in his own sin; nor can one become guilty for another, since the Lord forewarns us, saying, “The righteousness of the righteous shall be upon him, and the wickedness of the wicked shall be upon him.” And again: “The fathers shall not die for the children, and the children shall not die for the fathers. Every one shall die in his own sin.” Reading and observing this, we certainly think that no one is to be restrained from the fruit of satisfaction, and the hope of peace, since we know, according to the faith of the divine Scriptures, God Himself being their author, and exhorting in them, both that sinners are brought back to repentance, and that pardon and mercy are not denied to penitents.
Source: The Epistles of Cyprian (New Advent)