2 Chronicles 5:13
It came even to pass, as the trumpeters and singers were as one, to make one sound to be heard in praising and thanking the LORD; and when they lifted up their voice with the trumpets and cymbals and instruments of musick, and praised the LORD, saying, For he is good; for his mercy endureth for ever: that then the house was filled with a cloud, even the house of the LORD;
The verse describes the formal dedication of Solomon's temple to Jehovah and His worship after several years of building, taking place in the seventh month at the feast of tabernacles. The dedication followed the bringing of the wilderness tabernacle with its holy furniture, including the ark of the testament, to the temple. A great congregation from every part of the kingdom was gathered at Jerusalem, including the hosts of Israel and richly clad representatives of many foreign nations assembled before the temple.
At that gathering Solomon faced the great altar of burnt offering. The priests who had carried the sacred furniture had come out of the holy place to their places in the court. The Levitical singers arrayed in white linen with cymbals and psalteries and harps stood at the east end of the altar with one hundred and twenty priests sounding with trumpets. As the trumpeters and singers joined as one to make one sound in praising and thanking the Lord with trumpets and cymbals and instruments of music, declaring His goodness and enduring mercy, the house of the Lord was filled with a cloud.
The cloud was the glory of the Lord filling the house of God, the sign and presence of the Lord glorifying the temple at its dedication, so that the priests could not stand to minister. It signified divine acceptance and that the Lord had come to dwell in the thick darkness in the house Solomon had built as a habitation and dwelling place for Him forever. The temple's later outward splendor did not mean that God was still present there.