i.e. Which altar. But that he had now said, 2 Chronicles 1:5, and therefore would not unnecessarily repeat it. Or rather, who; and so these words are emphatical, and contain a reason why Solomon went thither, because the Lord was there graciously present to hear prayers and receive sacrifices.
Related Commentaries of 2 Chronicles 1:6
2 Chronicles 1:6
6 And Solomon went up thither to the brasen altar before the LORD, which was at the tabernacle of the congregation, and offered a thousand burnt offerings upon it.