السيرة
Saint Jerome wrote to us about him in his book "On Illustrious Men."
Archelaus was bishop of Kashkar in Mesopotamia. He was known for his holiness and his learning. He has a book containing a disputation between himself and the heretic Mani, who was from the land of Persia—he who established the "Manichaean" heresy, of which we have already spoken in the introduction to this book. This book was translated into Greek and was very famous in the days of Saint Jerome.
As for the story of this book, it is that a Syrian man practiced Christianity in deed and freed all his Christian slaves, since he felt that slavery is incompatible with the life of faith. Perhaps this practice was common among many of the masters who embraced the Christian faith, for they could not endure the humiliation of a brother of theirs in humanity after they had been touched by the surpassing love of God that raises them to sonship with God; so they would set their slaves free. And when many of them wished to work for them, they would receive them as laborers in a spirit of human brotherhood. This did not come about by ecclesiastical commands and canons, but rather it came about through the working of the Holy Spirit in the lives of the true believers.
When Mani heard about this Syrian man, Marcellus, he sent to him congratulating him on his act so full of love, intending thereby to draw him over to his heresy. But Marcellus sent to his bishop Archelaus, informing him of the matter. And here the bishop intervened to expose the errors of Mani, and a written dialogue took place between the bishop and Mani.
The West celebrates the feast of this bishop's repose on the 26th of December