Albert Barnes Commentary 1 Chronicles 22:1

"Then David said, This is the house of Jehovah God, and this is the altar of burnt-offering for Israel." — 1 Chronicles 22:1 (ASV)

This is the house of the Lord God — The double miracle—that of the angelic appearance and that of the fire from heaven—had convinced David that here he had found the destined site of that “house” which he had been told his son should build (1 Chronicles 22:10). Hence, this public announcement.