Ps 50:15

“"O Lord, my lips You shall open, and my mouth shall tell of Your praise" [Psalm 51:15]. "Your praise," because I have been created: "Your praise," because sinning I have not been forsaken: "Your praise," because I have been admonished to confess: "Your praise," because in order that I might be secured I have been cleansed.”

“"O Lord, you shall open my lips." It should be known that sometimes a person is impeded from teaching even by an interior impediment to speaking; and this happens sometimes because of the fault of the hearers. Ezek. 3: "I will make your tongue cleave to your palate, and you shall be mute." And below: "Because the house is exasperating." And because of his own sin. Ps. 106: "All iniquity shall stop its mouth." Because therefore God alone made the tongues of infants eloquent, Wis. 10, he therefore asks: Lord, remove the impediments which I have incurred through sin from my lips. And you, "open my lips." Eph. 6: "That speech may be given me in the opening of my mouth, to make known with confidence the mystery of the Gospel." It should be noted that in the opening of the mouth, the depth of teaching is understood wherever it is found in the Scriptures, as Job 3: "After this, Job opened his mouth." And Mt. 5: "Jesus, opening his mouth," namely in the depth of Scripture. "And then my mouth shall announce your praise"; as if to say: what I have in my heart, I will confess with my mouth.”

“Thee. The sinner cannot testify his gratitude better, than by promoting the conversion of others. (Worthington) — This is a sort of satisfaction. (Menochius) — While engaged in sin, David could not well exhort his subjects to repentance. His example was rather an inducement for them to transgress. (Berthier)— But when they saw his grief, and knew that God had pardoned him, they were no longer tempted to despair. He also watched more carefully over their conduct.”