Ambrose of Milan
Catena Aurea · Lukasevangelium 1
And there appeared unto him an angel of the the Lord standing on the right side of the altar of incense. And when Zacharias saw him, he was troubled, and fear fell upon him. But the angel said unto him, Fear not, Zacharias: for thy prayer is heard; and thy wife Elisabeth shall bear thee a son, and thou shalt call his name John. And thou shalt have joy and gladness; and many shall rejoice at his birth.
But a saint is not only the blessing of his parents, but also the salvation of many; as it follows, And many shall rejoice at his birth. Parents are reminded here to rejoice at the birth of saints, and to give thanks. For it is no slight gift of God to vouchsafe unto us children, to be the transmitters of our race, to be the heirs of succession.