Cyril of Alexandria

To them therefore it was not granted to know the mysteries of the kingdom of heaven, but rather unto us, who are more ready to embrace the faith. For He hath given unto us, as being perfect wisdom, the ability "to understand parables, and the dark saying, the words of the wise, and their riddles." For parables we may say are the images not of visible objects, but rather of those cognizable by the intellect and spiritual. …

Commentary on the Gospel of Luke, Sermon 41 ↗

Theophylact of Ohrid

For it was God Who made them to see, that is, to understand what is good. But they themselves see not, of their own will making themselves not to see, lest they should be converted and correct themselves, as if they were displeased at their own salvation. It goes on, Lest at any time they should be converted, and their sins be forgiven them. Or we may understand in a different way His speaking to the rest in parables, that seeing they might not perceive, and hearing, not understand. …

Catena Aurea by Aquinas ↗

Augustine of Hippo

And accordingly the very thing that seemed to be spoken by Himself in secret, was in a certain sense not spoken in secret; for it was not so spoken to remain unuttered by those to whom it was spoken; but rather so in order to be preached in every possible direction. …

Tractates On John 113 ↗