Chapter 5 — Part I: The Creed — Article III: Who Was Conceived by the Holy Ghost, Born of the Virgin Mary
Section 4. The Word, which is a Person of the Divine Nature, assumed human nature in such a manner that there should be one and the same Person in both the divine and human natures. Hence this admirable union preserved the actions and properties of both natures; and as Pope St. Leo the Great said: The lowliness of the inferior nature was not consumed in the glory of the superior, nor did the assumption of the inferior lessen the glory of the superior.