Augustine of Hippo

"His discourses have been softened above oil, and themselves are darts" [Psalm 55:21]. For certain things in the Scriptures were seeming hard, while they were obscure; when explained, they have been softened. For even the first heresy in the disciples of Christ, as it were from the hardness of His discourse arose. …

Exposition on Psalm 55 ↗

Gregory the Dialogist

Moreover there is this by the great favour of Almighty God; that among those who are divided from the doctrine of Holy Church there is no unity, since every kingdom divided against itself shall not stand. And holy Church is always more thoroughly equipped in her teaching when assaulted by the questionings of heretics; so that what was said by the Psalmist concerning God against heretics is fulfilled, "They are divided from the wrath of his countenance, and his heart hath drawn nigh." For while they are divided in their wicked error, …

Register of Epistles (Book VIII), Epistle II ↗