Augustine of Hippo

But yet, "hope in the Lord," is as yet expressed without explanation. Now what is hoped for, but good things? But since each one would obtain from God that good, which he loves; and they are not easy to be found who love interior goods, that is, which belong to the inward man, which alone should be loved, but the rest are to be used for necessity, not to be enjoyed for pleasure; excellently did he subjoin, when he had said, "hope in the Lord" [Psalm 4:6], "Many say, Who shows us good things?" This is the speech, and this the daily …

Exposition on Psalm 4 ↗

Bede

But because a human being lost this radiance of the divine countenance by sinning, it pleased God to assume the condition of a human countenance by being born in the flesh, in order that he might thereby teach us that we ought to be reborn in the Spirit. It pleased him to appear without sin in the likeness of sinful flesh so that he might cleanse us thoroughly from every sin and form again in us the distinctness of his image.

Homilies on the Gospels 1:6 ↗

Thomas Aquinas

Then when he says, "Many," he raises the question which the "many," that is, the foolish, ask: and they say, "Who shows us good things?" As if to say: how can we know what these sacrifices acceptable to God are? He resolves this question when he says: "The light of your countenance, O Lord, is sealed upon us"; as if to say: natural reason implanted in us teaches us to discern good from evil; and therefore he says, "The light of your countenance, O Lord, is sealed upon us," etc. …

Exposition on the Psalms of David ↗