Theophylact of Ohrid

"His mercy" is not upon Me alone, but also upon all who fear Him; for those who do not fear Him, being utterly unworthy, do not receive mercies. Having said that God's mercy is "from generation to generation," She indicated that those who fear God receive mercy both in the present generation, that is, in the present age, and in the future generation, that is, in the endless age; for here too they "receive a hundredfold," and there even more (Matt. 19:29).

Commentary on Luke ↗

Ancient Greek Expositor

According to the mercy which He hath upon generations of generations, I conceive, and He Himself is united to a living body, out of mercy alone undertaking our salvation. Nor is His mercy shown indiscriminately, but upon those who are constrained by the fear of Him in every nation; as it is said, upon those who fear him, that is, upon those who being brought by repentance are turned to faith and renewal for the obstinate unbelievers have by their sin shut against themselves the gate of mercy.

Catena Aurea by Aquinas ↗

Bede

And His mercy is on those who fear Him from generation to generation. Turning from His special gifts to the general judgments of God, he describes the state of the entire human race and explains alternately what the proud deserve, what the humble deserve, what the children of Adam have by free will, and what the children of God are by grace. Therefore, he says, He who is mighty has not done great things only for me, but also in every nation and generation, he who fears Him and works righteousness is accepted by Him.

On the Gospel of Luke ↗

Bonaventure

And his mercy, etc. After the affection of the one praising and the reason for praising have been described, here is added thirdly the amplification of divine praise. And this consists in the commendation of divine mercy with respect to the work of human redemption, already begun in the conception of the Virgin. …

Commentary on Luke, Chapter 1 ↗