1 Chronicles 27:23 indicates sufficiently why the numbering was sinful. It is also stated in 1 Chronicles 21:6, that Joab purposely omitted Levi and Benjamin from the reckoning.

Eight hundred thousand ... five hundred thousand - In Chronicles the numbers are differently given. It is probable therefore that the Chronicler has included in his statement of the sum total some numbers which are not included here.

In Israel eight hundred thousand - the men of Judah were five hundred thousand - In the parallel place, 1 Chronicles 21:5, the sums are widely different: in Israel one million one hundred thousand, in Judah four hundred and seventy thousand. Neither of these sums is too great, but they cannot be both correct; and which is the true number is difficult to say. The former seems the most likely; but more corruptions have taken place in the numbers of the historical books of the Old Testament, than in any other part of the sacred records. To attempt to reconcile them in every part is lost labor; better at once acknowledge what cannot be successfully denied, that although the original writers of the Old Testament wrote under the influence of the Divine Spirit, yet we are not told that the same influence descended on all copiers of their words, so as absolutely to prevent them from making mistakes. They might mistake, and they did mistake; but a careful collation of the different historical books serves to correct all essential errors of the scribes. See the Dissertations of Dr. Kennicott mentioned at the conclusion of the preceding chapter.

And Joab gave up the sum of the number of the people unto the king,.... Having collected from the several captains employed in this work their several particular numbers, he put them together, and gave in the sum total to David:

and there were in Israel eight hundred thousand valiant men that drew the sword; though many of them might be under the age of twenty, yet being robust and tall, and fit to bear arms, though but sixteen, seventeen, eighteen, or nineteen years of age, were mustered, contrary to the law; which, according to Cornelius Bertram (z) was David's sin, see 1 Chronicles 27:23. In 1 Chronicles 21:5, they are said to be a million and an hundred thousand, which is three hundred thousand more than the sum here given; several methods are taken to reconcile this; but what seems to be the best solution of the difficulty is what is observed by a Jew (a), that here the number of the people in the several parts of the land of Israel was given, which were eight hundred thousand, there along with them, the numbers of the standing army which waited on the king in their courses, which were twenty four thousand every, month, and amounted in the twelve months to 288,000, and reckoning lo thousand officers to them, they make the sum of three hundred thousand wanted, see 1 Chronicles 27:1, &c.

and the men of Judah were five hundred thousand men. In 1 Chronicles 21:5, they are said to be only 470,000, thirty thousand less than here; which may be accounted for by making use of a round number, though something wanting, as is often done; or else the thirty companies, consisting of a thousand each, under the eighty captains mentioned in 2 Samuel 23:8, are taken into the account here, but left out in the book of Chronicles; or there were so many in the sum total of the men of Judah before the plague, but thirty thousand being consumed thereby, are left out in the latter accounts, so Kimchi; but the other solutions seem best: Levi and Benjamin were not counted; it being abominable to Joab, he did not finish it, and especially being displeasing to God, who smote Israel for it, 1 Chronicles 21:6.

(z) Lucubrat. Frauktall, c. 2.((a) R. Eliezer in Halicot Olam, tract. 4. c. 3. p. 181.

And Joab gave up the sum of the number of the people unto the king: and there were in Israel {d} eight hundred thousand valiant men that drew the sword; and the men of Judah were {e} five hundred thousand men.

(d) According to Joab's count: for in all there were eleven hundred thousand, 1Ch 21:5.

(e) Including the Benjamites with them, or else they had but four hundred and seventy thousand.

[1] in Israel

Cf. 1Chr 21:5. The total military strength of Israel (the northern kingdom) was 1,100,000, and of Judah 500,000. The numbers actually set in array were, of Israel, 800,000; of Judah, 470,000.

9. Joab gave up the sum of the number of the people unto the king-The amount here stated, compared with 1Ch 21:5, gives a difference of three hundred thousand. The discrepancy is only apparent, and admits of an easy reconciliation; thus (see 1Ch 27:1-15), there were twelve divisions of generals, who commanded monthly, and whose duty was to keep guard on the royal person, each having a body of troops consisting of twenty-four thousand men, which, together, formed an army of two hundred eighty-eight thousand; and as a separate detachment of twelve thousand was attendant on the twelve princes of the twelve tribes mentioned in the same chapter, so both are equal to three hundred thousand. These were not reckoned in this book, because they were in the actual service of the king as a regular militia. But 1Ch 21:5 joins them to the rest, saying, "all those of Israel were one million, one hundred thousand"; whereas the author of Samuel, who reckons only the eight hundred thousand, does not say, "all those of Israel," but barely "and Israel were," &c. It must also be observed that, exclusive of the troops before mentioned, there was an army of observation on the frontiers of the Philistines' country, composed of thirty thousand men, as appears from 2Sa 6:1; which, it seems, were included in the number of five hundred thousand of the people of Judah by the author of Samuel. But the author of Chronicles, who mentions only four hundred seventy thousand, gives the number of that tribe exclusive of those thirty thousand men, because they were not all of the tribe of Judah, and therefore he does not say, "all those of Judah," as he had said, "all those of Israel," but only, "and those of Judah." Thus both accounts may be reconciled [Davidson].

24:1-9 For the people's sin David was left to act wrong, and in his chastisement they received punishment. This example throws light upon God's government of the world, and furnishes a useful lesson. The pride of David's heart, was his sin in numbering of the people. He thought thereby to appear the more formidable, trusting in an arm of flesh more than he should have done, and though he had written so much of trusting in God only. God judges not of sin as we do. What appears to us harmless, or, at least, but a small offence, may be a great sin in the eye of God, who discerns the thoughts and intents of the heart. Even ungodly men can discern evil tempers and wrong conduct in believers, of which they themselves often remain unconscious. But God seldom allows those whom he loves the pleasures they sinfully covet.