From a Sermon
In the meanwhile the evangelist says with firmness, “The Word was made flesh, and dwelt among us.” From this we learn that the angel, when he saluted the Virgin with the words, “Hail, you that are highly favoured, the Lord is with you,” intended to signify God the Word is with you, and also to show that He would arise from her bosom, and would be made flesh, even as it is written, “The Holy Ghost shall come upon you, and the power of the Highest shall overshadow you; therefore also that holy thing which shall be born of you shall be called the Son of God.”
Source: Fragments (New Advent)