2 Samuel 24:8-10

8At the end of nine months and twenty days, having gone through the whole land, they returned to Jerusalem. 9And Joab reported to the king the total number of the troops. In Israel there were 800,000 men of valor who drew the sword, and in Judah there were 500,000.

10After David had numbered the troops, his conscience was stricken and he said to the LORD, “I have sinned greatly in what I have done. Now, O LORD, I beg You to take away the iniquity of Your servant, for I have acted very foolishly.”