The angels’ reaction to the birth of Christ . . .

The baby was born in a stable, not in a palace. It was laid in a feeding trough for animals, not in a pretty bassinet. All this spells poverty, deprivation . . . These angels, having been associated with Christ in heaven before his incarnation, knew something about his glory, riches, and majesty. They had also become aware of man’s fall. And they had been informed that God had provided a way of salvation for man. Gabriel’s announcement to Joseph—“You shall call his name Jesus, for he will save his people from their sins” (Matt. 1:21)—clearly implies this.
Did they also know that this work of saving man, while at the same time fully maintaining God’s righteousness, meant that the Father would not spar his own Son: that the Son, thought he was rich, for his people’s sake would become poor, vicariously bearing the curse resting on those whom he came to save; and that the Holy Spirit would condescend to dwell in sinful hearts, applying to them the salvation merited by the Son. We can assume at least that the very birth of Christ in a condition of poverty and deprivation must have caused these angels to stand in awe of God’s indescribably marvelous love.
The Gospel of Luke
 ~ William Hendriksen