Jeremy Cushman recently asked if one of the writers on this blog would be willing to address the use of Is. 40.3 in Mt. 3.3 (see here). He wanted to know if the wilderness language was being correctly applied by John the Baptist in his proclamation (and I assume we ought to examine the evangelist’s use as well). Also, he wanted to know if John’s proclamation has anything to do with the Qumran community dwelling in the wilderness waiting for YHWH’s vindication. I am willing to provide one take and I’d welcome others.
I will order my approach this way: (1) historical setting; (2) literary context; (3) dogmatic function.
Historical context: Many scholars have suggested that John the Baptist may have derived from the Qumran community. He was in the wilderness. He seems to have been in protest of both the Jerusalem hierarchy as well as the corrupt temple cult. He was willing to suggest that forgiveness of sins could come from YHWH God without the sacrificial system and ritual washings offered by the priesthood, but rather his own ministry near the Jordan River would suffice.
Did he actually come from Qumran? I don’t know if there is any way to know. That Is. 40.3 would have been read by the people of Qumran as evidence that YHWH’s return will come in the wilderness (rather than in the city) is likely, though I cannot think of any DSS texts off the top of my head that say this (any suggestions, anyone?).
It does seem that John himself may have very well adopted this passage to refer to his own ministry. Now when we ask if John used this text legitimately we are asking a tough question. Who is to say? Did the author of Isaiah 40 have John in mind? Unlikely. Did John stand in the hermeneutical tradition of early Judaism that had no qualm with applying biblical texts to the current situation. Yes.
So no, Is. 40.3 likely does not refer directly to the Qumran community or John’s ministry. This does not make the usage illegitimate though. It seems to be a common hermeneutic in this time that YHWH God reenacts his own works (see how often the exodus tradition is reenacted). John could have seen his own ministry as reenacting YHWH’s return in the wilderness and it seems even more likely that this is exactly how the evangelist interpreted it.
Literary context: So what did Matthew mean by this? It is commonly suggested that this is a good proof text for the incarnation. Again, yes and no. I doubt that John saw Jesus and he thought, “Oh, look, YHWH as a man!” Rather, I would bet that he understood his own ministry as a prophet as calling Israel back to covenant faithfulness in order for the presence of YHWH God to return (as N.T. Wright would say, this would be the “forgiveness of sins” and “the end of exile”).
When Matthew connects Jesus he may or may not have thought something like developed Christian doctrine when we speak of the incarnation. Rather, it seems that the first evangelist understood Jesus as bringing YHWH’s presence in his ministry. To borrow from Wright again, in the tradition of Psalm 2 and 110, the Messiah represents YHWH’s reign on earth. While Matthew may not have thought of Jesus as being YHWH “incarnate” as later language would suggest, he surely did see Jesus as embodying YHWH’s returning reign. In Jesus we have YHWH’s return to Israel.
Dogmatic function: Is it wrong to read Mt. 3.3 as a “fulfillment” of Is. 40.3 that Jesus would be YHWH incarnate, visiting his people. May we maintain this dogma? I say yes. While Mt. 3.3. may not have originally insinuated this, we still formulate doctrine as the church catholic. We gain from the Johannine and Pauline writings that Jesus was “God made known in human existence” or “the Logos made flesh”. We are not part of a s0-called Matthean community that is only aware of the gospel from that perspective. We have the collected “canon” of the early church and therefore we do Christology broadly.
With that in mind it is the same Jesus in the First Gospel that we find in the Fourth Gospel. We need to let the first evangelist have his voice, but we should stop with saying that Jesus embodied YHWH’s presence and acted on behalf of YHWH because the First Gospel may seem to be saying no more or no less (this is debated). We do our dogmatics, once again, from a catholic perspective. So we can read Mt. 3.3. and think about Jesus being God incarnate and it is right to do so. This doesn’t necessitate that the first evangelist intend such a thing.
the archives near Emmaus 
A very fair and careful consideration of the text.
It seems that John’s focus with his ministry wasn’t so much on where the way was being prepared, but rather that it was being prepared (even though I would have to agree with you in that he still fulfills Is. 40:3 because Jesus is baptized in the wilderness as a sort of inaugurating for Jesus’ ministry).
We’ve only read through one document from the Dead Sea Scrolls in my class and from the tone of it, assuming this was the community who inhabited the Qumran ruins, they did a lot of things in a strict manner. I would have to imagine that they believed the Messiah would emerge from their own community because they were faithful to God and located in the wilderness.
They also believed in an extreme predestination; everyone was predestined to either be a son of light or a son of darkness. There was no cross over. John, if he did emerge from this community, obviously left it because he believed people could change – or at the very least he believed that he could help them return to the predestined path God wanted them on. His style of ministry would not have been accepted within the community of Qumran, but I don’t think he really cared. I mean, he was eating locusts and wild honey for crying out loud.
@Jeremy: It is possible that John saw this passage as referring to his own prophetic ministry in the wilderness. If not that, we do have the evangelist making the connection. I am only agnostic about whether or not he gained this from the Qumran community or not.
It does appear that Qumran saw God being victorious through their community and the Messiah being connected to them some how. As the sons of light they were to participate in YHWH’s judgement on apostate Israel and the pagans. I assume Messiah would lead.