Bede

For behold, as soon as the sound of your greeting reached my ears, the child leaped for joy in my womb. Elizabeth was embarrassed by the burden of pregnancy as long as she did not know the mystery of the religion. But she who hid herself because she had conceived a son began to boast because she was bearing a prophet. And she who was previously embarrassed now blesses, and she who doubted before is now affirmed. For behold (she says), as soon as the sound of your greeting reached my ears, the child leaped for joy in my womb. …

On the Gospel of Luke ↗

Bonaventure

Secondly she adds an approbative indication, when she says: For behold, as soon as the voice of your greeting sounded in my ears, the infant in my womb leapt for joy: and this is a sign that "grace is poured forth upon your lips"; and therefore it is certain that "God has blessed you forever," in the Psalm. And since the infant leapt beyond nature, it is certain that the Lord of nature came to meet him. …

Commentary on Luke, Chapter 1 ↗