Theophylact of Ohrid

As at the silence of Zacharias the people marvelled, so likewise when he spoke. Hence it is said, And fear came upon all; that from these two circumstances all might believe there was something great in the child that was born. But all these things were ordained, to the end that he who was to bear witness of Christ might also be esteemed trustworthy. Hence it follows, And all they that heard them laid them up in their heart, saying, What manner of child, &c.

Catena Aurea by Aquinas ↗

Ancient Greek Expositor

For God worked miracles in John which he did not himself, but the right hand of God in him.

Catena Aurea by Aquinas ↗

Bede

And these words were spread over all the mountains of Judaea. And all those who heard them laid them up in their hearts, saying: What will this child be? For the hand of the Lord was with him. Great are the works of the Lord, exquisite in all his desires (Psalm 110). Behold, the silence of Zacharias alone, given to him as a punishment for disbelief and as a sign of belief, not only benefits him when it is taken away, but it also astounds all his neighbors with the miracle and fear. …

On the Gospel of Luke ↗

Bonaventure

Second, he adds the reverence of the miracle, when he says: And fear came upon all their neighbors, and throughout all the hill country of Judea all these words were spread abroad: the Psalm: "All who dwell at the borders shall fear at your signs"; whence they could sing that of Exodus 15: "Who is like you among the mighty, O Lord? …

Commentary on Luke, Chapter 1 ↗

Glossa Ordinaria

But mystically, at the time of our Lord's resurrection, by the preaching of the grace of Christ, a wholesome dread shook the hearts not only of the Jews, (who were neighbours, either from the place of their dwelling, or from the knowledge of the law,) but of the foreign nations also. The name of Christ surmounts not only the hilly country of Judæa, but all the heights of worldly dominion and wisdom.

Catena Aurea by Aquinas ↗