2 Samuel 24:8-10

8When they had covered the whole country, they came to Jerusalem after 9 months and 20 days.

9Joab reported the census figures to the king: In Israel there were 800,000 able-bodied men who could serve in the army, and in Judah there were 500,000.

10After David counted the people, his conscience troubled him. David said to the Lord, “I have committed a terrible sin by what I have done. Lord, please forgive me because I have acted very foolishly.”