Psalms 51:1 «To the chief Musician, A Psalm of David, when Nathan the prophet came unto him, after he had gone in to Bathsheba. » Have mercy upon me, O God, according to thy lovingkindness: according unto the multitude of thy tender mercies blot out my transgressions.
A Psalm of David] Who was not ashamed to do open penance here in a white sheet, as it were; so did Theodosius the emperor, at the reprehension of Ambrose, after the slaughter at Thessalonica; he spent eight months, saith Theodoret, in weeping and lamentation; he fell down on his face in the place of the penitents, and said, My soul is glued to the earth, &c. Henry IV (then king of Navarre only, afterwards of France also), having abused the daughter of a gentleman in Rochel, by whom he had a son, was persuaded by Monsieur Du-Plessis to make a public acknowledgment of his fault in the church, which also he did before all the nobility of his army. This counsel being thought by some to be too rigorous, Du-Plessis made this answer, That as a man could not be too courageous before men, so he could not be too humble in the presence of God (Life of Phil. de Morn., by Mr Clark).
When Nathan the prophet came unto him] Rousing him out of a long lethargy, into which sin and Satan had cast him. See here the necessity of a faithful ministry, to be to us as the pilot was to Jonah, as the cock to Peter, &c.; as also of a friendly admonitor, such as David had prayed for, Psalms 141:5, and here he is answered. David had lain long in sin without repentance to any purpose; some remorse he had felt, Psalms 32:3, but it amounted not to a godly sorrow, till Nathan came; and in private, dealing plainly with him, more prevailed than all the lectures of the law or other means had done all that while.
After he had gone in to Bathsheba] This was the devil's nest-egg that caused many sins to be laid, one to and upon another. See the woeful chain of David's lust, 2 Samuel 11:1,27; 2 Samuel 12:1,25, and beware.
Ver. 1. Have mercy upon me, O God] It was wont to be, O my God, but David had now sinned away his assurance, wiped off his comfortables; he dares not plead propriety in God, nor relation to him, as having forfeited both. At another time, when he had greatly offended God by numbering the people, God counted him but plain David, "Go and say to David," 2 Samuel 24:12, whereas before, when he purposed to build God a temple, then it was, "Go tell my servant David," 2 Samuel 7:5. Sin doth much impair and weaken our assurance of God's favour; like as a drop of water falling on a burning candle dimmeth the light thereof. The course that David taketh for recovery of this last evil is confession of sin, and hearty prayer for pardoning and purging grace. In the courts of men it is safest (saith Quintilian) to plead Non feci, Not guilty; not so here, but Ego feci, miserere miserrimi peccatoris, misericors Deus. Guilty, Lord, have mercy, &c.
Per miserere mei tollitur ira Dei.
According to the multitude of thy tender mercies] They are a multitude of them, and David needeth them all, for the pardon of his many and mighty sins; that where sin had abounded grace might superabound, it may have a superpleonasm, 1 Timothy 1:14 .
Blot out my transgressions] Out of thy debtbook; cross out the black lines of my sins with the red lines of Christ's blood; cancel the bond, though written in black and bloody characters.