Charles Ellicott Commentary 1 Chronicles 21:20

"And Ornan turned back, and saw the angel; and his four sons that were with him hid themselves. Now Ornan was threshing wheat." — 1 Chronicles 21:20 (ASV)

And Ornan turned back ( returned ) , and saw the angel; and his four sons with him hid themselves (were hiding). There can be little doubt that this is corrupt, and that the text of Samuel is right, And Araunah looked up, and saw the king and his servants passing by him. The Septuagint here has Ornan turned, and saw the king; the Vulgate, when Ornan had looked up. The Hebrew words for “returned” and “looked up,” “angel” and “king,” are similar enough to be easily confused in an ill-written or failed manuscript.

Now Ornan was threshing wheat. —This clause does not harmonize with the preceding statement, but its genuineness is made probable by the fact that Ornan was in his threshingfloor at the time. Moreover, the Septuagint adds to 2 Samuel 24:15, And David chose for himself the death; and it was the days of wheat harvest.