David is here under the rod for numbering the people, that rod of correction which drives out the foolishness that is bound up in the heart, the foolishness of pride. Let us briefly observe,
I. How he was corrected. If God's dearest children do amiss, they must expect to smart for it. 1. He is given to understand that God is displeased; and that it is no small uneasiness to so good a man as David, Ch1 21:7. God takes notice of, and is displeased with, the sins of his people; and no sin is more displeasing to him than pride of heart: nor is anything more humbling, and grieving, and mortifying to a gracious soul, than to see itself under God's displeasure. 2. He is put to his choice whether he will be punished by war, famine, or pestilence; for punished he must be, and by one of these. Thus, for his further humiliation, he is put into a strait, a great strait, and has the terror of all the three judgments impressed upon his mind, no doubt to his great amazement, while he is considering which he shall choose. 3. He hears of 70,000 of his subjects who in a few hours were struck dead by the pestilence, Ch1 21:14. He was proud of the multitude of his people, but divine Justice took a course to make them fewer. Justly is that taken from us, weakened, or embittered to us, which we are proud of. David must have the people numbered: Bring me the number of them, says he, that I may know it. But now God numbers them after another manner, numbers to the sword, Isa 65:12. And David had another number of them brought, more to his confusion than was to his satisfaction, namely, the number of the slain - a black bill of mortality, which is a drawback to his muster-roll. 4. He sees the destroying angel, with his sword drawn against Jerusalem, Ch1 21:16. This could not but be very terrible to him, as it was a visible indication of the anger of Heaven, and threatened the utter destruction of that beloved city. Pestilences make the greatest devastations in the most populous places. The sight of an angel, though coming peaceably and on a friendly errand, has made even mighty men to tremble; how dreadful then must this sight be of an angel with a drawn sword in his hand, a flaming sword, like that of the cherubim, which turned every way to keep the way of the tree of life! While we lie under the wrath of God the holy angels are armed against us, though we see them not as David did.
II. How he bore the correction. 1. He made a very penitent confession of his sin, and prayed earnestly for the pardon of it, Ch1 21:8. Now he owned that he had sinned, had sinned greatly, had done foolishly, very foolishly; and he entreated that, however he might be corrected for it, the iniquity of it might be done away. 2. He accepted the punishment of his iniquity: "Let thy hand be on me, and on my father's house, Ch1 21:17. I submit to the rod, only let me be the sufferer, for I am the sinner; mine is the guilty head at which the sword should be pointed." 3. He cast himself upon the mercy of God (though he knew he was angry with him) and did not entertain any hard thoughts of him. However it be, Let us fall into the hands of the Lord, for his mercies are great, Ch1 21:13. Good men, even when God frowns upon them, think well of him. Though he slay me, yet will I trust in him. 4. He expressed a very tender concern for the people, and it went to his heart to see them plagued for his transgression: These sheep, what have they done?

David said - I am in a great strait - The Targum reasons thus:
"And David said to Gad, If I choose famine, the Israelites may say, The granaries of David are full of corn; neither doth he care should the people of Israel die with hunger. And if I choose war, and fly before an enemy, the Israelites may say, David is a strong and warlike man, and he cares not though the people of Israel should fall by the sword. I am brought into a great strait; I will deliver myself now into the Hand of the Word of the Lord, ביד מימרא דיי beyad meymera dayai, for his mercies are many; but into the hands of the children of men I will not deliver myself."

See Chapter Introduction
See Chapter Introduction
1 Chronicles 21:28

ch1 21:28
ch1 21:28
ch1 21:28At that time when David saw that the Lord had answered him in the threshing floor Of Ornan the Jebusite,.... The same with Araunah, Sa2 24:16, with some small variation of the letters, and are of the same signification; both signifying the "ornus", as Hillerus (m) observes, the pine tree or ash; see Isa 44:14, in whose threshingfloor David now was, and where he had been praying and sacrificing; and God had accepted his prayer, as the Targum, and had answered him, by causing fire to come down on the sacrifice and consume it, and by ordering the angel to put up his sword in its sheath:

then he sacrificed there; again by the priests, and continued to do so, for he had sacrificed there before, Ch1 21:26 and finding his sacrifices in that place were acceptable, he repeated them, and did not go to Gibeon, as follows.

(m) Onomastic. Sacr. p. 529, 530.

let me fall now into the hand of the Lord . . . let me not fall into the hand of man--Experience had taught him that human passion and vengeance had no bounds, whereas our wise and gracious Father in heaven knows the kind, and regulates the extent, of chastisement which every one needs.