In this letter (translated into Latin by Jerome) Dionysius, bishop of Lydda, praises Theophilus for his signal victories over Origenism and urges him to continue his efforts against that heresy. Written in 400 a.d.
Reproduced in full. Translation: Nicene and Post-Nicene Fathers, series 2, vol. 6 (Schaff and Wace, 1893), public domain (Public domain).