IX. An exhortation to accept the Catholic view of the Incarnation.
Give up, my sons, give up these suggestions of the devil. God's Truth nothing can impair, but the Truth does not save us except in our flesh. For, as the prophet says, “truth is sprung out of the earth,” and the Virgin Mary conceived the Word in such wise that she ministered flesh of her substance to be united to Him without the addition of a second person, and without the disappearance of her nature: seeing that He who was in the form of God took the form of a slave in such wise that Christ is one and the same in both forms: God bending Himself to the weak things of man, and man rising up to the high things of the Godhead, as the Apostle says, “whose are the fathers, and from whom, according to the flesh is Christ, who is above all things God blessed for ever. Amen.”
Source: Letters (New Advent)