Albert Barnes Commentary 2 Chronicles 3:1

"Then Solomon began to build the house of Jehovah at Jerusalem on mount Moriah, where [Jehovah] appeared unto David his father, which he made ready in the place that David had appointed, in the threshing-floor of Ornan the Jebusite." — 2 Chronicles 3:1 (ASV)

Where the Lord appeared to David - The marginal rendering, or “which was shown to David,” is preferred by some. The expression is understood to point out to David the proper site for the temple by the appearance of the angels and the command to build an altar (2 Samuel 24:17–25; 1 Chronicles 21:16–26).

In the place that David had prepared - This seems to be the true meaning of the passage, though the word order in the original text has been accidentally disordered.