2 Samuel 24:8-10

8So when they had gone throughout all the land, they came back to Jerusalem at the end of nine months and 20 days.

9Joab reported the sum of the numbering of the people to the king: there were in Israel 800,000 valiant men who drew the sword and the men of Judah were 500,000 men.

10But David’s heart troubled him after he had numbered the people. So David prayed to Adonai, “I have sinned greatly in what I have done! But now, Adonai, please take away the iniquity of Your servant, for I have acted very foolishly.”