Adam Clarke on Luke 2:13

Suddenly there was with the angel, etc. - this multitude of the heavenly host had just now descended from on high, to honor the new-born Prince of peace, to give his parents the fullest conviction of his glory and excellence, and to teach the shepherds, who were about to be the first proclaimers of the Gospel, what to think and what to speak of him, who, while he appeared as a helpless infant, was the object of worship to the angels of God.