Augustine of Hippo

"The mouth of the righteous speaketh wisdom" (ver. 30). See here is that "bread." Observe with what satisfaction this righteous man feedeth upon it; how he turns wisdom over and over in his mouth. "And his tongue talketh of judgment."

Exposition on Psalm 37 ↗

Ambrose of Milan

When he established the just moral disciplines, to teach you what kind you ought to be, and what would be the perfect form of justice; he wants his mind to rise to wisdom and theorems; and arouse his intention, so that he may look at heavenly things with an attentive heart, and revolve the divine oracles within himself, and direct his affection towards those things which please God: let him meditate on the Law, and let no commandments of the Lord escape him; let him recognize the movement of the divine …

Commentaries on the Twelve Davidic Psalms ↗

Thomas Aquinas

"The mouth of the just shall meditate." Here he shows that the goods of the just are greater with regard to the exercise of virtue, because the unjust have a mouth prone to evil. First, therefore, he treats of the spiritual goods of the just. Second, of the perversity of the wicked, at "He watches." Regarding the first, he does two things. First, he sets forth the spiritual goods in which the just excel. …

Exposition on the Psalms of David ↗