The Lord said - he would dwell - It was under the appearance of a cloud that God showed himself present with Israel in the wilderness; see Exodus 14:19, Exodus 14:20. And at the dedication of the tabernacle in the wilderness, God manifested himself in the same way that he did here at the dedication of the temple; see Exodus 40:34, Exodus 40:35.
Rather, “The Lord spake of dwelling in the thick darkness” (margin reference). Solomon sees in the cloud the visible symbol of God‘s presence, and accepts the token as a proof that He has taken possession of the house built for Him, and will thenceforth dwell there 1 Kings 8:13.