Athanasius of Alexandria

But every one rejoiced in the nativity of Christ, not with human feelings, as men are wont to rejoice when a son is born, but at the presence of Christ and the lustre of the Divine light. As it follows: And the shepherds returned, glorifying and praising God for every thing they had heard, &c.

Catena Aurea by Aquinas ↗

Theophylact of Ohrid

The shepherds returned with thanksgiving to God for all things; for they were not envious like the Jews.

Commentary on Luke ↗

Bede

And the shepherds returned, glorifying and praising God for all the things they had heard and seen, as it was told unto them. The shepherds glorify and praise God for all the things they had heard from the angels, and seen in Bethlehem, as it was told unto them, that is, they glorify also in this, that upon coming they found nothing else than what had been told unto them; or as it was told unto them, they give glory and praise to God. …

On the Gospel of Luke ↗

Bonaventure

And the shepherds returned etc. Here the diligence of the shepherds is commended on account of the gratitude of devotion. For devotion to be acceptable to God, it is necessary that the hand, the mind, and the tongue resound and harmonize together: the hand by working, the tongue by praising, the mind by recognizing. The devotion of the shepherds was therefore praiseworthy on account of due operation, by reason of which it is said: The shepherds returned, namely to the custody of the flock entrusted to them. …

Commentary on Luke, Chapter 2 ↗