Go up, rear an altar unto the Lord - This place is supposed to be Mount Moriah: on which, according to the rabbins, Cain and Abel offered their sacrifices; where Abraham attempted to sacrifice Isaac, and where the temple of Solomon was afterwards built.

And Gad came that day to David,.... Ordered and directed by the angel of the Lord, Ch1 21:18,

and said unto him, go up, rear an altar unto the Lord in the threshing floor of Araunah the Jebusite: it was too far to go to Gibeon, where the tabernacle was, at such a time of extremity, when the sword of the angel was stretched out over Jerusalem, Ch1 21:29; and this was the most proper place, as it was the very spot over and nearest to which the angel was; and was on Mount Moriah, where the Jews say Abraham offered up Isaac; and where the temple was afterwards built, as Kimchi and Ben Gersom observe; and Eupolemus, an Heathen writer (g), says, that when David desired to build a temple for God, and that he would show him the place of the altar, an angel appeared to him, standing over the place where the altar at Jerusalem was to be built.

(g) Apud Euseb. Evangel. Praepar. l. 9. c. 30. p. 447.

Araunah--or Ornan (Ch1 21:18), the Jebusite, one of the ancient inhabitants, who, having become a convert to the true religion, retained his house and possessions. He resided on Mount Moriah, the spot on which the temple was afterwards built (Ch2 3:1); but that mount was not then enclosed in the town.