By Water & Blood

Book 1, Chapter 14: That the Church rightly rejected Marcellus for holding the same as Sabellius

Fittingly, then, the Church, proclaiming these things, rejected Sabellius as one who had counterfeited a spurious coin—the denial of the Son of God—even though he said, just as Marcellus does, that he knew one God and that there is none besides him. And the first heralds of our Saviour himself named “Ebionites”—calling them in the Hebrew tongue “poor” in understanding—those who said that they knew one God and did not deny the Saviour’s body, but did not know the Godhead of the Son.

And the Samosatene too, although he taught that Jesus is the Christ of God and confessed, just as Marcellus does, the one God who is over all, the ecclesiastical fathers declared alien to the Church of God, because he did not confess that Christ was also Son of God and God before his birth in the flesh. But he was driven far from the Church as one who acted impiously toward Christ;

while Sabellius, as one who offended against the Father himself, whom he dared to call Son, underwent the same punishment as the godless heretics. And Marcellus, suspecting that he would suffer the same as he, devised a newer contrivance for his error, defining God and the Word in him as one, while granting him the two titles of Father and Son. Yet he did not escape notice, nor get away, but was at length caught in his own nets;

except that even before he was caught, stricken in conscience, he set out to blaspheme Sabellius in order to put away the suspicion.