You are doing the works your father did.” They said to him, “We were not born of fornication. We have one Father—even God” (Jn 8:41).
i) Critics of the virgin birth complain that this event is only reported in two sources: Matthew and Luke. Actually, the fact that we have two independent records of this event is impressive.
But now I'd like to consider a neglected source. It's possible or probable that Jn 8:41 is an indirect allusion to the virgin birth. If so, that's even more impressive because it represents hostile testimony.
ii) Of course, Jesus' Jewish opponents didn't believe in the virgin birth. The question, rather, is whether, in Jn 8:41, they are alluding to his out-of-wedlock conception. They don't construe that as a virginal conception, but a virginal conception would underlie and account for his out-of-wedlock conception.
iii) Scholars are divided on whether his opponents are questioning his legitimacy. For instance, Keener says:
Because Jesus' interlocutors in the story would here, like most of his interlocutors in the Gospel, interpret him too literally, they may take his charge as implying that they do in fact stem from an adulterous union. Alternatively, they could understand "fornication" in its spiritual sense referring to idolatry. C. Keener, The Gospel of John: A Commentary (Hendrickson 2003), 1:759.
But if they took him literally, then, by parity of argument, we'd expect the charge of illegitimacy to be literal. So it's unclear why Keener raises that in objection to the interpretation in question.
And, of course, the figurative interpretation is incompatible with the literal interpretation, so we need to decide which is preferable. he can't list both options as a cumulative objection to the interpretation in question.
Keener also says his opponents are on the defensive at this point, and only go on the offensive in v48. But it's not clear what that means. They seem to be responding to Jesus with a counter-allegation. "We are not bastards"–which carries the implicitly invidious comparison to Jesus.
Indeed, it's a rhetorical trap. By using suggestive language that leaves the comparison implicit, it attempts to create a dilemma for Jesus. If he declines to respond, the slur does its damage by default. It's out there, to injure his reputation.
If, however, he does respond, he must acknowledge the rumor to refute it. In a way, that confirms the rumor–though not the defamatory interpretation.
Finally, Keener says:
It is not clear that such charges were sufficiently widespread by the end of the first century to be assumed by John's audience or that of his tradition (although this is possible). Ibid. 1:759.
But there are problems with that objection:
i) We need to distinguish between John's audience and the historical audience. Jesus is addressing some Jews, in the early thirties. John repeats this because that's what they said. He's recording this exchange because the larger dialogue is important to establish the person and work of Christ. Even if this particular allusion would escape their ken, that's embedded in a crucial dialogue.
ii) John may well expect his readers to have background information from prior Gospels. He can take for granted their awareness of the virgin birth. Even if every reader didn't know that, it's not his responsibility. The supplementary information is available.
Meier thinks the reference is figurative, like the reference to Samaritan pedigree in v48. Cf. J. Meier, A Marginal Jew (Doubleday 1991), 1:228-29.
However, the Samaritan comparison is obscure. Commentators struggle with what his accusers had in mind. Moreover, that allegation is combined with the allegation of demonic possession, which may well be literal.
If 7:41 is a literal slur, that that generates a dilemma for the liberal view of John's Gospel. Liberals date this Gospel to the first quarter of the 2C. They think the author had no firsthand knowledge of the historical Jesus. They think he invented speeches whole cloth.
But in that event, why in the world would the narrator fabricate that defamatory innuendo? Why would he plant that idea in the mind of the reader? Why introduce that stigmatizing characterization into his narrative if it had no historical precedent? Why invent a weapon that critics would use against Jesus?
If, however, this is a historically accurate transcript (or summary) of an actual exchange, then it's plausible that Jesus' Jewish opponents would attempt to discredit him by calling him a (literal) bastard. If they had malicious gossip to that effect, they would surely use it at some point or another. And they'd place the least flattering interpretation on rumors that Mary was an unwed mother. I think many scholars are too high-minded to appreciate what enemies will resort to.
Indeed, the illegitimacy of Jesus became a standard element of the Jewish polemic. Origen responds to that. We find it in the Toledot Yeshua. In fact, that is still a part of the Jewish polemic, right down to our very own day:
My point is not that that these later sources reflect independent traditions. Rather, they represent a hostile interpretation of the virgin birth.
By the same token, it's easy to see how the virgin birth would give rise to similar allegations by spiteful neighbors–who'd be more than happy to share that with the Jewish authorities in Jerusalem.