Notes on the Bible, by Albert Barnes, , at sacred-texts.com
The resemblance to the parallel passage in Samuel is throughout less close than usual; the additions are more numerous, the supernatural circumstances of the narrative being brought out into greater prominence. The history is evidently not drawn from Samuel, but from some quite separate document, probably a contemporary account of the occurrence drawn up by Gad.
1 Chronicles 21:1
As the books of Scripture are arranged in our Version, Satan is here for the first time by name introduced to us. He appears not merely as an "adversary" who seeks to injure man from without, but as a Tempter able to ruin him by suggesting sinful acts and thoughts from within. In this point of view, the revelation made of him here is the most advanced that we find in the Old Testament.
The difficulty in reconciling the statement here, "Satan provoked David," etc. with that of Samuel, "the Lord moved David," etc. Sa2 24:1 is not serious. All temptation is permitted by God. When evil spirits tempt us, they do so by permission (Job 1:12; Job 2:6; Luk 22:31, etc.). If Satan therefore provoked David to number the peopIe, God allowed him. And what God allows, He may be said to do. (Another view is maintained in the Sa2 24:1 note).
1 Chronicles 21:5
In Sa2 24:9 the numbers are different. The explanation there given is not so generally accepted as the supposition that the numbers have, in one passage or the other (or possibly in both), suffered corruption.
1 Chronicles 21:6
To omit the Levites would be to follow the precedent recorded in Num 1:47-49. The omission of Benjamin must he ascribed to a determination on the part of Joab to frustrate the king's intention, whereby he might hope to avert God's wrath from the people.
1 Chronicles 21:12
And the angel of the Lord destroying ... - These words are not in Samuel, which puts the third alternative briefly. They prepare the way for the angelic appearance Ch1 21:16, on which the author is about to lay so much stress.
1 Chronicles 21:16
Here a picture of awful grandeur takes the place of the bare statement of the earlier historian Sa2 24:17. And here, as elsewhere, the author probably extracts from the ancient documents such circumstances as harmonize with his general plan. As the sanctity of the temple was among the points whereon he was most anxious to lay stress, he gives in full all the miraculous circumstances attending this first designation of what became the temple site (marginal reference "k") as a place "holy to the Lord."
David and the elders ... clothed in sackcloth, fell upon their faces - Facts additional to the narrative of Samuel; But facts natural in themselves, and in harmony with that narrative. Similarly, the narrative in Ch1 21:20 is additional to the account in Samuel; but its parts hang together; and there is no sufficient ground for suspecting it.
1 Chronicles 21:18
It has been observed that it is only in books of a late period that Angels are brought forward as intermediaries between God and the prophets. This, no doubt, is true; and it is certainly unlikely that the records, from which the author of Chronicles drew, spoke of Gad as receiving his knowledge of God's will from an angel. The touch may be regarded as coming from the writer of Chronicles himself, who expresses the fact related by his authorities in the language of his own day (see Zac 1:9, Zac 1:14, Zac 1:19; Zac 2:3; Zac 4:1; Zac 5:5; etc.); language, however, which we are not to regard as rhetorical, but as strictly in accordance with truth, since Angels were doubtless employed as media between God and the prophet as much in the time of David as in that of Zechariah.
1 Chronicles 21:25
Compare the marginal reference and note. It may also be conjectured that we should read "six" for "six hundred" here; since, according to the later Jewish system, six gold shekels were nearly equal in value to fifty silver ones.
1 Chronicles 21:26
He answered him from heaven by fire - This fact is not mentioned by the author of Samuel, since his object is to give an account of the sin of David, its punishment, and the circumstances by which that punishment was brought to a close, not to connect those circumstances with anything further in the history. With the writer of Chronicles the case is different. He would probably have omitted the whole narrative, as he did the sin of David in the matter of Uriah, but for its connection with the fixing of the temple site 1 Chr. 22. It was no doubt mainly the fact that God answered him by fire from heaven on this altar, which determined David, and Solomon after him, to build the temple on the spot so consecrated.
1 Chronicles 21:30
David, knowing that by sacrifice on this altar he had caused the angel to stay his hand, was afraid to transfer his offerings elsewhere, lest the Angel should resume his task and pestilence again break out.