3 “O you sons of men, how long heavy in heart”. 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. For, “vanity is of deceivers, and all is vanity.” “What profit has a man of all his labour, wherewith he labours under the sun?” Why then are you held back by the love of things temporal? Why follow ye after the last things, as though the first, which is vanity and a lie? For you would have them abide with you, which all pass away, as does a shadow.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)