Augustine of Hippo

"O you sons of men, how long heavy in heart" [Psalm 4:2]. Let your error, says he, have lasted at least up to the coming of the Son of God; why then any longer are you heavy in heart? When will you make an end of crafty wiles, if now when the truth is present ye make it not? "Why do ye love vanity, and seek a lie?" Why would ye be blessed by the lowest things? Truth alone, from which all things are true, makes blessed. …

Exposition on Psalm 4 ↗

Thomas Aquinas

Then when he says, "O sons," etc., he turns to the exhortation of others: and concerning this he does two things. First he rebukes sinners; second he exhorts them to amendment, at "And know," etc. Concerning the first he does two things. First he recalls their condition; second he charges their fault, at "Why do you love"; he recalls their condition saying, "sons of men": which can be understood in two ways. First in a bad sense, thus: "sons of men," as if men according to their lower nature, corruptible and prone to sin. Gen. …

Exposition on the Psalms of David ↗

Bonaventure

"O sons of men, how long will you be heavy of heart? Why do you love vanity and seek after falsehood? And know that the Lord has made His Holy One wonderful: the Lord will hear me when I cry to Him. Be angry, and do not sin: for what you say in your hearts, upon your beds be moved to compunction." He who has true knowledge and knows God and sees that he does not walk rightly or perfectly is in continual sorrow, because he sees that his affections and thoughts are scattered. Augustine: "Knowledge begets mourning."

Collationes de Septem Donis, Collation 4 ↗