And, lo, the angel of the Lord came upon them He says, that the glory of the Lord [1] shone around the shepherds, by which they perceived him to be an angel. [2] For it would have been of little avail to be told by an angel what is related by Luke, if God had not testified, by some outward sign, that what they heard proceeded from Him. The angel appeared, not in an ordinary form, or without majesty, but surrounded with the brightness of heavenly glory, to affect powerfully the minds of the shepherds, that they might receive the discourse which was addressed to them, as coming from the mouth of God himself. Hence the fear, of which Luke shortly afterwards speaks, by which God usually humbles the hearts of men, (as I have formerly explained,) and disposes them to receive his word with reverence.

Footnotes

1 - "La clarte du Seigneur;" -- "the brightness of the Lord."

2 - "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."

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, etc. 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.

The angel of the Lord came upon them - Or, stood over them, επεστη. It is likely that the angel appeared in the air at some little distance above them, and that from him the rays of the glory of the Lord shone round about them, as the rays of light are projected from the sun.
They were sore afraid - Terrified with the appearance of so glorious a being, and probably fearing that he was a messenger of justice, coming to denounce Divine judgments, or punish them immediately, for sins with which their consciences would not fail, on such an occasion, to reproach them.

And, lo, the angel of the Lord (e) came upon them, and the glory of the Lord shone round about them: and they were sore afraid.
(e) Came suddenly upon them, when they were not at all thinking about such a matter.

And lo, the angel of the Lord,.... It may be Gabriel, who had brought the tidings of the conception of the Messiah to the virgin, and now the birth of him to the shepherds:
came upon them; on a sudden, unexpectedly, at once, and stood by them, as some versions read; or rather, stood over them, over their heads, just above them; so that he was easily and perfectly seen by them,
and the glory of the Lord shone round about them; or a very glorious and extraordinary light shone with surprising lustre and brightness all around them; by which light, they could discern the illustrious form of the angel that was over them:
and they were sore afraid; at the sight of such a personage, and at such unusual light and glory about them: they were not used to such appearances, and were awed with the majesty of God, of which these were symbols, and were conscious to themselves of their own sinfulness and frailty.

glory of the Lord--"the brightness or glory which is represented as encompassing all heavenly visions" [OLSHAUSEN].
sore afraid--So it ever was (Daniel 10:7-8; Luke 1:12; Revelation 1:17). Men have never felt easy with the invisible world laid suddenly open to their gaze. It was never meant to be permanent; a momentary purpose was all it was intended to serve.

The angel of the Lord. An angel announces the conception of Jesus; a host of angels publish his birth; in his temptation an angel strengthens him; in his agony an angel comforts him; at his resurrection an angel rolls away the stone from the door of the sepulcher; at his ascension the angels attend him up to heaven; and at his second coming to judge the world he shall be "revealed from heaven with his mighty angels."