John Calvin 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)

And, lo, the angel of the Lord came upon them. Luke says that the glory of the Lord¹⁴⁵ shone around the shepherds, and by this glory they perceived him to be an angel.¹⁴⁶

For it would have been of little use to be told by an angel what Luke relates, if God had not testified by some outward sign that what they heard came from Him.

The angel appeared, not in an ordinary form or without majesty, but surrounded with the brightness of heavenly glory, to powerfully affect the minds of the shepherds so that they might receive the message addressed to them as coming from the mouth of God himself.

Hence the fear, of which Luke soon after speaks, and by which God usually humbles the hearts of men, (as I have previously explained), and prepares them to receive his word with reverence.

¹⁴⁵ “La clarte du Seigneur;” — “the brightness of the Lord.”;” — “the brightness of the Lord.”

¹⁴⁶ “c'a este afin qu'ils cogneussent que c'estoit l'ange de Dieu qui parloit;” — “it was in order that they might know that it was the angel of the Lord that spoke.”;” — “it was in order that they might know that it was the angel of the Lord that spoke.”