Pray, tell me, why the Spirit of God descended into a woman’s womb at all, if He did not do so for the purpose of partaking of flesh from the womb. For He could have become spiritual flesh without such a process,—much more simply, indeed, without the womb than in it. He had no reason for enclosing Himself within one, if He was to bear forth nothing from it. Not without reason, however, did He descend into a womb. Therefore He received (flesh) therefrom; else, if He received nothing therefrom, His descent into it would have been without a reason, especially if He meant to become flesh of that sort which was not derived from a womb, that is to say, a spiritual one.
Tertullian
On the Flesh of Christ
Chapter XIX