Augustine of Hippo

Accordingly, what the soul supplies to the body, and what God supplies to the soul, are of a different kind: the soul quickens and is quickened. It quickens while dead, even if itself is not quickened. But when the word comes, and is poured into the hearers, and they not only hear, but are made obedient, the soul rises from its death to its life—that is, from unrighteousness, from folly, from ungodliness, to its God, who is to it wisdom, righteousness, light. Let it rise to Him, and be enlightened by Him. …

Tractates on John 19 ↗

Ambrose of Milan

Therefore, He fittingly substitutes: 'For with you is the fountain of life: and in your light we shall see light.' Extend your mercy to those who know you, and your righteousness to those who are upright in heart. Indeed, after the remembrance of heavenly benefits, gratitude is rightly ascribed to our Lord Jesus Christ, who, as the life-giving fountain of eternity, descended to earth to water the dryness of our hearts. …

Commentaries on the Twelve Davidic Psalms ↗

Thomas Aquinas

"And in your light." There are two privileges of the rational creature. One is that the rational creature sees in the light of God, and because other animals do not see in the light of God, he therefore says "in your light." This is not understood of light created by God, because in that sense it would be understood as that which is said in Gen. 1: "Let there be light." But "in your light," namely that by which you shine, which is the likeness of your substance. …

Exposition on the Psalms of David ↗