Apparently the census was complete before David acknowledged that he had sinned. Finally guilt for his pride penetrated his heart, and he confessed his sin and asked God for forgiveness (v. 10). This response shows David at his best, as "the man after God's own heart."God graciously gave the king some choice about how He would punish the nation (v. 13). I believe that this is the only instance in Scripture where God gave someone the option of choosing his own punishment. Because David was the head of the nation his actions affected all Israel as well as himself personally. David's choice was whether he wanted a long, mild punishment or a short, intense one. He chose to leave the punishment in God's hands because he had learned that God is merciful (v. 14).
"War would place the nation at the mercy of its enemies: famine would make it dependent on corn-merchants, who might greatly aggravate the misery of scarcity: only in the pestilence--some form of plague sudden and mysterious in its attack, and baffling the medical knowledge of the time--would the punishment come directly from God, and depend immediately upon His Will."324
The rabbis assumed that David's reasoning was as follows.
"If I choose famine the people will say that I chose something which will affect them and not me, for I shall be well supplied with food; if I choose war, they will say that the king is well protected; let me choose pestilence, before which all are equal."325
(NT only) to listen to the NET Bible 
