St. Augustine: "Heretics"

“THEY are heretics who in the Church of God entertain some unwholesome and perverse opinion, and on being rebuked refuse to alter it and square it to sound and right doctrine, but are contumacious in their resistance, refuse to amend their pestilential and deadly creed, and persist in defending the same.”

~St. Augustine: The City of God, 18, 51.

Conversion of the Heretic (scene 15, east wall), by Benozzo Gozzoli.
Fresco, 1464-65; Apsidal chapel, Sant'Agostino, San Gimignano.