To Dionysius of Rome (Eus., H. E. vii. 7, 6 and 8) (The fourth letter on Baptism)

For with Novatian we are reasonably indignant, seeing that he has cut the Church in two and dragged certain of the brethren into impieties and blasphemies and introduced the most unholy teaching about God and accuses the most gracious Jesus Christ our Lord of being without pity, [98] and besides all this sets at nought the holy laws and overthrows the confession of faith before baptism, [99] and altogether banishes the Holy Spirit from them, even though there were some hope of His remaining or even of His returning to them. [100]