Jamieson, Fausset and Brown on 2 Samuel 12:7

7. Nathan said to David, Thou art the man--These awful words pierced his heart, aroused his conscience, and brought him to his knees. The sincerity and depth of his penitent sorrow are evinced by the Psalms he composed (Psa 32:1-11; 51:1-19; 103:1-22). He was pardoned, so far as related to the restoration of the divine favor. But as from his high character for piety, and his eminent rank in society, his deplorable fall was calculated to do great injury to the cause of religion, it was necessary that God should testify His abhorrence of sin by leaving even His own servant to reap the bitter temporal fruits. David was not himself doomed, according to his own view of what justice demanded (2Sa 12:5); but he had to suffer a quadruple expiation in the successive deaths of four sons, besides a lengthened train of other evils.