Augustine of Hippo

If we wish to be guarded by Him who was humbled for our sakes, and who was exalted to keep us, let us be humble. Let no one assume anything unto himself. No man hath any good, except he hath received it from Him who alone is good. But he who chooseth to arrogate wisdom unto himself, is a fool. Let him be humble, that wisdom may come, and may enlighten him. But if, before wisdom cometh unto him, he imagine that he is wise; he riseth before light, and walketh in darkness. What doth he hear in this Psalm? …

Exposition on Psalm 127 ↗

Gregory the Dialogist

But what kind of fruit they ought to bring forth is added: "And your fruit should remain." Everything for which we labor according to the present age barely suffices until death. For death intervening cuts off the fruit of our labor. But what is done for eternal life is preserved even after death; and it begins to appear when the fruit of carnal labors has begun to disappear. Therefore, that reward begins where this one ends. Whoever therefore has already come to know eternal things, let temporal fruits become worthless in his soul. …

Forty Gospel Homilies, Homily 27 ↗

Bernard of Clairvaux

He whose gaze is held by the darkness cannot see the light. Bitterness holds him in its grip, the unpleasant recollection of his sins preoccupies his memory to the exclusion of every joyful thought. It is to souls like this that the Prophet says: "It is vain for you to rise before light." He points out that it is useless for you to aspire to the contemplation of truths that give delight, until the sins that disquiet you have been blotted out in the light of consolation.

Sermons on the Song of Songs, Sermon 10 ↗