Charles Ellicott Commentary 1 Chronicles 21:22

"Then David said to Ornan, Give me the place of this threshing-floor, that I may build thereon an altar unto Jehovah: for the full price shalt thou give it me, that the plague may be stayed from the people." — 1 Chronicles 21:22 (ASV)

Then (and) David said to Oman, Grant me the place of this threshingfloor, that I may build. —Literally, Pray give me the place of the threshingfloor. Samuel records: And Araunah said, “Why has my lord the king come to his servant?” And David said, “To purchase the threshingfloor from you, to build,” etc.

Grant it me for the full price. —Literally, At a full price give it me. These words are not in Samuel. (Compare Genesis 23:9—Abraham’s purchase of the Cave of Machpelah.) The recollection of that narrative may have caused the modification of the present. The last clause is word for word as in Samuel.