Adam Clarke on 2 Chronicles 6:1

The Lord hath said that he would dwell - Solomon, seeing the cloud descend and fill the house, immediately took for granted that the Lord had accepted the place, and was now present. What occurred now was precisely the same with what took place when Moses reared the tabernacle in the wilderness; see Exo 40:34, Exo 40:35 : A cloud covered the tent - and the glory of the Lord filled the tabernacle. And Moses was not able to enter into the tent - because the glory of the Lord filled the tabernacle.

The Chaldee paraphrases thus: "Then said Solomon, It has pleased God to place his majesty in the city of Jerusalem, in the house of the sanctuary which I have built to the name of his Word, and he hath placed a dark cloud before him.