The dedication of the Temple reaches its peak with a visible manifestation of the Divine presence. When a cloud fills the sanctuary, King Solomon experiences a profound realization. He understands that this is a clear sign that God has chosen to linger and rest His presence within the newly built Temple [רש"י, מצודת דוד, ביאור שטיינזלץ]. The profound thickness and density of the cloud vividly mark this arrival [מצודת דוד].
Solomon recognizes this event as part of a consistent historical pattern of Divine revelation. Just as the glory of God appeared from within a cloud during the days of the Tabernacle in the desert, it now returns to the permanent sanctuary [רד"ק]. A prominent example of this pattern is Mount Sinai, where Moses approached the thick cloud where God was present, confirming that this is His chosen method of revealing Himself [רש"י, מצודת דוד].
Furthermore, the appearance of the cloud is the direct fulfillment of an earlier promise. The Torah previously established that God would appear in a cloud over the cover of the Ark of the Covenant. While early traditions sometimes connect this promise to the smoke rising from the incense offering, the plain meaning points directly to the cloud of Divine glory. Seeing this cloud descend upon the Temple, Solomon is presented with absolute proof that God has kept His word, bringing His glory to rest in the permanent sanctuary exactly as He promised [רש"י, רד"ק].