Albert Barnes Commentary Luke 2:9

"And an angel of the Lord stood by them, and the glory of the Lord shone round about them: and they were sore afraid." — Luke 2:9 (ASV)

The glory of the Lord. This is the same as a great glory—that is, a splendid appearance or light. The word glory is often the same as light (1 Corinthians 15:41; Luke 9:31; Acts 22:11).

The words Lord and God are often used to denote greatness or intensity. Thus, trees of God mean great trees; hills of God, high or lofty hills, and so on. So the glory of the Lord here means an exceedingly great or bright luminous appearance—perhaps not unlike what Paul saw on the way to Damascus.