34 I remember that I have already discussed at sufficient length the question of "the temple of God," and how this saying is to be taken, "As many of you as have been baptized into Christ have put on Christ." For neither are the covetous the temple of God, since it is written, "What agreement has the temple of God with idols?" And Cyprian has adduced the testimony of Paul to the fact that covetousness is idolatry. But men put on Christ, sometimes so far as to receive the sacrament, sometimes so much further as to receive holiness of life. And the first of these is common to good and bad alike; the second, peculiar to the good and pious. Wherefore, if "baptism cannot be without the Spirit," then heretics have the Spirit also—but to destruction, not to salvation, just as was the case with Saul. For in the Holy Spirit devils are cast out through the name of Christ, which even he was able to do who was without the Church, which called forth a suggestion from the disciples to their Lord. Just as the covetous have the Holy Spirit, who yet are not the temple of God. For "what agreement has the temple of God with idols?" If therefore the covetous have not the Spirit of God, and yet have baptism, it is possible for baptism to exist without the Spirit of God.
35. If therefore heresy is rendered "unable to engender sons to God through Christ, because it is not the bride of Christ," neither can that crowd of evil men established within the Church, since it is also not the bride of Christ; for the bride of Christ is described as being without spot or wrinkle. Therefore either not all baptized persons are the sons of God, or even that which is not the bride can engender the sons of God. But as it is asked whether "he is spiritually born who has received the baptism of Christ in the midst of heretics," so it may be asked whether he is spiritually born who has received the baptism of Christ in the Catholic Church, without being turned to God in a true heart, of whom it cannot be said that he has not received baptism.
Source: On Baptism, Against the Donatists (New Advent)