Solomon is building this great Temple (house) for God. As the work is being completed God speaks to Solomon to remind him that He dwells among people not in a building.
It is as if God says, “Concerning the house…thanks, but don’t forget.” God wants the people to walk right, do right, and keep right more than he desires a this place Solomon is building. He is reminding Solomon that the new temple is not his religion, his spirituality, or his faith. God says, “I will dwell among you,” as if to remind them that is their religion.
The church building is special, but it doesn’t hold God.
The same holds true today. God dwells with believers in the person of the Holy Spirit. The church building is special, but it doesn’t hold God. He dwells with us who keep to His Word.