Charles Ellicott Commentary 2 Samuel 12:13

"And David said unto Nathan, I have sinned against Jehovah. And Nathan said unto David, Jehovah also hath put away thy sin; thou shalt not die." — 2 Samuel 12:13 (ASV)

I have sinned. —The same words were used by Saul (1 Samuel 15:24; 1 Samuel 15:30), but in a totally different spirit. Saul’s confession was a concession to the prophet for the purpose of securing his support, and with no real penitence; David, in these few words, pours out before God the confession of a broken heart.

Thou shalt not die. —David had committed two crimes for which the Law imposed the penalty of death—adultery (Leviticus 20:10) and murder (Leviticus 24:17). As an absolute monarch he had no reason to fear that the sentence would be put in force by any human authority; and the Divine word is to him of far more importance as an assurance of forgiveness than as a warding off of any possible earthly danger. The phrase is thus parallel to, and explanatory of, the previous clause, The Lord also hath put away thy sin.