The ultimate focus of the newly built Temple is the physical space holding the testimony of the relationship between God and His people. The primary approach among commentators is that bringing the Ark into the Temple represents the core purpose of the building, but the true significance lies in what the Ark actually contains.
Inside the Ark rest the tablets given to the Israelites when their special bond with God was first established. These tablets bear the engraved Ten Commandments, which capture the very essence of the entire Torah. Ultimately, they function much like a marriage contract presented by God at Mount Sinai, detailing the unique covenant formed between Him and the Israelites.