Thomas Aquinas, on Ps 50:10

“To my hearing thou shalt give joy and gladness: and the bones that have been humbled shall rejoice.”

“"A clean heart." Above, the Psalmist asked for sin to be removed; here he asks for the effects of sin to be removed, which are two: namely, the defilement of the soul and the disorder of the affections. The first effect occurs because a person is attached to earthly things; hence he asks for cleanness of heart. Mt. 5: "Blessed are the clean of heart, for they shall see God"; and therefore he says, "Create in me a clean heart, O God, and a right spirit." This cleanness of heart, God alone can restore. Job 14: "Who can make clean one conceived of unclean seed? Is it not you who alone are," namely, simply clean? And he says "create." Something is created unto the being of nature when it is produced from nothing into being. Gen. 1: "In the beginning God created," etc. Also when it is produced unto the being of grace. 1 Cor. 13: "If I should have prophecy, and should know all mysteries, etc., I am nothing" in the being of grace. But when God works by the operation of grace in one who has grace, he is said to magnify him. But when he makes a just person out of a sinner, then he is properly said to create. Eph. 2: "We are his workmanship, created in Christ Jesus in good works." Jas. 1: "That we might be some beginning of his creature," namely, his spiritual creature. The second thing that follows from sin is the disorder of the mind, which occurs through the turning away from the proper end. Therefore, just as through the turning to some changeable good the mind becomes unclean, so through the turning away from the end it becomes disordered; and the rectitude by which a person is directed toward God is opposed to this disorder. Song 1: "The upright love you"; and therefore he says, "and renew a right spirit," that is, grant anew, because I lost it through sin. Eph. 4: "Be renewed in the spirit of your mind." "And renew it" not outwardly, but "in my inward parts," so that not only my lips for speaking but my heart may be right for knowing.”

Imported from an open dataset — not yet checked against the printed edition.