pp.238-9:
Christ: Born Human
For the orthodox, Jesus' real humanity was guaranteed by the [proposition] that he was actually born, the miraculous circumstances surrounding that birth notwithstanding. This made the matter of Jesus' nativity a major bone of contention between orthodox Christian s and their docetic opponents. Marcion, as we have seen, denied Jesus' birth and infancy altogether. In response, Irenaeus could ask, "Why did He acknowledge Himself to be the Son of man, if He had not gone through that birth which belongs to a human being?" (Adv. Haer. IV, 33, 2). The question is echoed by Tertullian, who cites a number of passages that mention Jesus' "mother and brothers" and asks why, on general principles, it is harder to believe "that flesh in the Divine Being should rather be unborn than untrue? " (Adv. Marc. Ill, 11).
In light of this orthodox stand, it is not surprising to find the birth of Christ brought into greater prominence in texts used by the early polemicists. I can cite two instances. In both cases one could argue that the similarity of the words in question led to an accidental corruption. But it should not be overlooked that both passages proved instrumental in the orthodox insistence on Jesus' real birth, making the changes look suspiciously useful for the conflict.
In Galatians 4:4, Paul says that God "sent forth his Son, come from a woman, come under the law" (γενόμενον έκ γυναικός, γενόμενον ύπό υό μυν). The verse was used by the orthodox to oppose the Gnostic claim that Christ came through Mary "as water through a pipe," taking nothing of its conduit into itself; for here the apostle states that Christ was "made from a woman" (so Irenaeus, Adv. Haer. Ill, 22, 1, and Tertullian, de carne Christi, 20). Irenaeus also uses the text against docetists to show that Christ was actually a man, in that he came from a woman (Adv. Haer. V, 21, 1). It should strike us as odd that Tertullian never quotes the verse against Marcion, despite his lengthy demonstration that Christ was actually "born."
This can scarcely be attributed to oversight, and so is more likely due to the circumstance that the generally received Latin text of the verse does not speak of Christ's birth per se, but of his "having been made" (factum ex muliere).
Given its relevance to just such controversies, it is no surprise to see that the verse was changed on occasion, and in precisely the direction one might expect: in several Old Latin manuscripts the text reads: misit deus filium suum, natum ex muliere ("God sent his Son, born of a woman"), a reading that would have proved useful to Tertullian had he known it. Nor is it surprising to find the same change appear in several Greek witnesses as well, where it is much easier to make, involving the substitution of γεννώμενον for γενόμενον (K f1 and a number of later minuscules).
A similar corruption occurs in Romans 1:3-4, a passage I have already discussed in a different connection [see pp.71-2 [and p.48], next post below]. Here Paul speaks of Christ as God's Son "who came from the seed of David according to the flesh" (τον γενόμενον έκ σπέρματος Δαυιδ κατά σάρκα). The heresiologists of the second and third centuries also found this text useful for showing that Christ was a real man who was born into the world. Tertullian, for example , claims that since Christ is related to David (his seed) because of his flesh, he must have taken flesh from Mary (de carne Christi 22; cf. Irenaeus, Adv. Haer. Ill, 22,1). Given the orthodox assumption that "having come from the seed of David" must refer to Jesus' own birth—an event not actually described by Paul—one is not taken aback to find the text of Romans 1:3 changed [in] the second century, as attested by the citations of Origen, and periodically throughout the history of its transmission (61* syrpal, Byzmss OLmss acc to Aug).
As was the case with Galatians 4:4, the change was a matter of the substitution of a word in the versions and of a few simple letters in Greek (from γενόμενον to γεννώμενον), so that now the text speaks not of Christ "coming from the seed of David" but of his "being born of the seed of David."
p.242:
... several orthodox modifications speak directly to the physical dimension of Christ's existence (1 John 5:9, 20; Heb 2:14; Eph 5:30) or stress that he was "a man" (John 19:5; 7:46; Matt 8:27) or emphasize his real physical birth (Gal 4:4; Rom 1:3)