Charles Ellicott Commentary 1 Chronicles 21:5

"And Joab gave up the sum of the numbering of the people unto David. And all they of Israel were a thousand thousand and a hundred thousand men that drew sword: and Judah was four hundred threescore and ten thousand men that drew sword." — 1 Chronicles 21:5 (ASV)

The number. — Muster, or census (miphqăd). The first clause is identical with Samuel, but has “David” for “the king,” as elsewhere.

And all they of Israel. — And all Israel became (came to). The numbers are different in Samuel, which states them as 800,000 for Israel and 500,000 for Judah. The latter may fairly be regarded as a round number (500,000), our text giving the more exact total (470,000).

Regarding the former, we may assume that the 1,100,000 of our text is an error of transcription, or, more probably, that the traditions concerning this census varied, as may easily have happened, because the numbers were not registered in the royal archives (1 Chronicles 27:24). Perhaps, however, our estimate includes the standing army of David, reckoned (1 Chronicles 27:1–15) at a total of 288,000 men (in round numbers, 300,000); thus 800,000 (Samuel) + 300,000 = 1,100,000 (Chronicles).