Albert Barnes Commentary 1 Kings 8:11

"so that the priests could not stand to minister by reason of the cloud; for the glory of Jehovah filled the house of Jehovah." — 1 Kings 8:11 (ASV)

As in the case of Moses (Exodus 40:35), so now the glory of the Lord—the manifestation of the divine presence, which the cloud usually veiled—shone forth from it with such brilliance that mortal man could not bear the sight.