That Christ is both man and God, compounded of both natures, that He might be a Mediator between us and the Father
In Jeremiah: And He is man, and who shall know Him? Also in Numbers: “A Star shall arise out of Jacob, and a man shall rise up from Israel.” Also in the same place: “A Man shall go forth out of his seed, and shall rule over many nations; and His kingdom shall be exalted as Gog, and His kingdom shall be increased; and God brought Him forth out of Egypt. His glory is as of the unicorn, and He shall eat the nations of His enemies, and shall take out the marrow of their fatnesses, and will pierce His enemy with His arrows.
He couched and lay down as a lion, and as a lion's cub. Who shall raise Him up? Blessed are they who bless You, and cursed are they who curse You.” Also in Isaiah: “The Spirit of the Lord is upon me; on account whereof He has anointed me: He has sent me to tell good tidings to the poor; to heal the bruised in heart, to preach deliverance to the captives, and sight to the blind, to proclaim the acceptable year of the Lord, and the day of retribution.” Whence, in the Gospel according to Luke, Gabriel says to Mary: “And the angel, answering, said to her, The Holy Ghost shall come upon you, and the power of the Highest shall overshadow you.
Wherefore that holy thing which is born of you shall be called the Son of God.” Also in the first Epistle of Paul to the Corinthians: “The first man is of the mud of the earth; the second man is from heaven. As was he from the soil, such are they also that are of the earth; and as is the heavenly, such also are the heavenly. As we have borne the image of him who is of the earth, let us also bear the image of Him who is from heaven.”
Source: The Treatises of Cyprian (New Advent)