I found this on a Reformed Baptist's blog. I really like the way he translates Augustine here: it's spot on for a sermon.

“Righteousness has looked down from heaven. in order that people may have a righteousness which is not their own, but God’s…

Unless He had a human birth, we would never attain to the divine rebirth; He was born that we might be reborn. Let nobody hesitate to be reborn; Christ has been born; born with no need of being reborn. The only ones in need of rebirth are those who have been condemned in their first birth.

And so let His mercy come to be in our hearts. His mother bore Him in her womb; let us bear Him in our hearts. The virgin was big with the incarnation of Christ; let our bosoms grow big with the faith of Christ. She gave birth to the Savior; let us give birth to praise. We mustn’t be barren; our souls must be fruitful with God.

The birth of Christ from the Father was without mother; the birth of Christ from his mother was without father; each birth was wonderful. The first was eternal, the second took place in time. When was He born of the Father? What do you mean, when? You’re asking about “when” there where you won’t find any time? Don’t ask about “when” there. Ask about it here; it’s a good question, when was He born of His mother. When was He born of the Father is not a good question. He was born, and He has no time; He was born eternal, from the eternal, co-eternal. Why be astonished? He’s God. Take divinity into consideration, and any reason for astonishment disappears.

And when we say He was born of a virgin, it’s a great thing, you’re astonished. He’s God, don’t be astonished; let astonishment give way to thanksgiving and praise. Let faith be present; believe that it happened. If you don’t believe, it still happened, but you remain unbelieving. He agreed to become man; what more do you want? Hasn’t God humbled Himself enough for you? The one who was God has become man.”

— St. Augustine, sermon # 189