John Gill Bible Commentary

And Araunah said, wherefore is my lord the king come to his servant?.... Which both implies admiration in him, that so great a person should visit him in his threshingfloor; that a king should come to a subject his servant, who should rather have come to him, and would upon the least intimation; it was a piece of condescension he marvelled at; and it expresses a desire to know his pleasure with him, supposing it must be something very urgent and important, that the king should come himself upon it: and to this David made answer: and David said, what he was come for: to buy the threshingfloor of thee, to build an altar to the Lord, that the plague may be stayed from the people; for though David had acknowledged his sin, and God had repented of the evil he inflicted for it, and given orders for stopping it; yet he would have an altar built, and sacrifices offered, to show that the only way to have peace, and pardon, and safety from ruin and destruction, deserved by sin, is through the expiatory sacrifice of Christ, of which fill sacrifices were typical, and were designed to lead the faith of the Lord's people to that.