John Chrysostom

But he who earns favour in the sight of God has nothing to fear. Hence it follows, For thou hast found favour before God. But how shall any one find it, except through the means of his humility. For God giveth grace to the humble. (James 4:6, 1 Pet. 5:5.)

Catena Aurea by Aquinas ↗

Gregory of Nyssa

While the expectation of child-birth strikes a woman with terror, the sweet mention of her offspring calms her, as it is added, And thou shall call his name Jesus. The coming of the Saviour is the banishing of all fear.

Catena Aurea by Aquinas ↗

Theophylact of Ohrid

The Angel, first of all, calms Her heart from fear, so that She might receive the divine response in an undisturbed state; for in a state of confusion she could not properly hear what was about to come to pass — then, as if in explanation of the aforementioned word "Full of grace," he says: "You have found favor with God." For to be graced means to receive grace from God, that is, to please God. …

Commentary on Luke ↗

Bede

And the angel said unto her, Fear not, Mary, for thou hast found favor with God. Having seen that she was troubled by an unusual greeting, as it were, which was kept for her alone, calling her more familiarly by her name, he bids her not to fear. And because he had called her full of grace, he further establishes that grace and explains it more abundantly, saying:

On the Gospel of Luke ↗

Bonaventure

Therefore the Angel, expressing the good pleasure of divine acceptance, strengthens and addresses the Virgin by name: Fear not, Mary. Fear not, I say, but rejoice, because your name is written in heaven, according to what is said below to the Apostles, in chapter ten: "Rejoice that your names are written in the heavens." And he gives the reason: For you have found grace with God, the grace, namely, of election, as Moses: Exodus 33: "You have found grace before me, and I have known you by name"; so it is said to the Virgin Mary. …

Commentary on Luke, Chapter 1 ↗