You're right about so many things. I'm glad we're having this conversation. I would point to how Matthew arrives at what is prophecy. In Mt. 1.23, he quotes Isa. 7.14, but that verse had no place in Jewish messianic expectation. Isaiah most likely saw nothing more than that a woman of his era would have a son, and that after a few years Ahaz would be delivered from Syria and Israel with the coming of the Assyrians. But Matthew, fully convinced that Mary was a virgin when she delivered Jesus (and there would be little rationale to invent it for many reasons), sees that prophecy "filled up" as he applies it to Jesus. In Mt. 2.6, he doesn't quote the MT or the LXX directly as he "quotes" Micah 5.2, but does a wordplay on the word "ruler" to heighten the status he is attributing to Jesus as a ruler. In 2.15 he quotes Hos. 11.1, which also was not intended by the prophet as a prediction. Hosea was reflecting on history and talking about the nation of Israel, but Matthew "fills up" the verse, giving it a prophetic flag, and using it as a "type" of the Messiah, whom he identifies as Jesus. But there is some justification in his doing that, because Numbers 24 speaks of a king of Israel coming out of Egypt (Num. 24.7-9), which appears to be partly alluded to in Hos. 11.10-11.

So you are absolutely right that there is nothing important to Messianic prophecy concerning him being a Nazarene, or about him taking a vow, except that Matthew's thesis (whether or not you agree with it) is that Jesus, as Messiah, fulfills everything that Israel failed to be: He is the new Israel, the new Law, the new Moses, etc. He is portrayed as the Branch of David, Abraham's true son, the great deliverer out of Egypt, etc. It wouldn't surprise me at all that Matthew wants to depict him as the one wholly devoted to God, the branch of Jesse, or the guardian of Jer. 31.6. I don't see an inconsistency in what Matthew is trying to do.

As far as Zechariah 4.14, there is widespread agreement that the two "sons of oil" are Zerubbabel and Joshua, governing ruler and high priest. The interpretation of the two "olive branches" as two messiahs doesn't emerge until the era of Qumran and apocalyptic literature in the 200s or so BC. Zech. 3.8 confirms that Zechariah spoke of the Branch as a singular entity.

As far as my citing rabbinical practice, it was fair of me to do that. Jesus even commended the Pharisees for their righteousness. They were the backbone of Judaism, eager students of the Law, and avid teachers of it. Jesus admitted they spoke the truth (Mt. 23.2-3), but he challenged them when their behavior failed to match their teachings. He praised them for their zeal, their desire to avoid evil, and their faithfulness in tithing. what he castigated them for is their hypocrisy, so I thought my use of that practice to explain Matthew's approach was legitimate. Jesus' rebuke of them doesn't nullify their exegetical techniques.

I don't buy that. Because there is nothing important to Messianic prophecy concerning him being a Nazarene. I believe they thought there was so they put that in there. But they were completely wrong. Nazirite practice is not necessary in the least for the Messiah. Those same rabbinical sources point to him actually coming from outside of Israel. See the story of Moshiach at the Gates of Rome.

And it is funny that you mention a rabbinical practice for your reasoning. This is because rabbinical Judaism is basically Pharasaic Judaism, the people Jesus condemned more than anyone.

The Branch (Isa. 11.1) does refer to the Messiah. But all that the Branch means is that it grows from the root of Jesse. And why is the Messiah called "the Branch?" It is because he/they are likened to two olive trees in Zechariah 4.
1. And I raised my voice a second time and said to him, "What are the two olive branches beside the two golden vats that empty out the gold[en oil] from themselves?"
2. And he spoke to me, saying, "Do you not know what these are?" And I said, "No, my lord."
3. And he said, "These are the two anointed ones who stand before the Lord of all the earth."

See? There are two anointed ones. I will tell you that this is the Prince and the Priest. Jews today believe it refers to something else, but you have to take the text as it stands and not fit it to your own understanding.

But we can concede the previous point regarding him being a Nazarene. But I would just say that nowhere does the OT say anything about the Messiah being one who takes a vow.

Oh, excellent choice. Thank you for such a good discussion. I appreciate it. Before we go to Mt. 2.23, I want to refer you to a rabbinical practice (since Matthew was Jewish) where biblical passages are frequently interpreted through slightly different grammatical forms, differing from anything found in the texts that we have. For instance, in Avoth 6.2 we are taught about Ex. 32.16 ("And the tablets were the work of God, and the writing was the writing of God, graven upon the tablets"), but the teaching of the rabbi is, "Do not read haruth (graven) but rather heiruth (freedom), for no person is free except one who engages in the study of Torah." Matthew is most likely using a similar approach here. He is using the liberty of the rabbinical practice of wordplay to make his point.

You are absolutely correct in saying that there is no prophecy in the Old Testament that the Messiah will be a Nazarene. Notice also that Matthew says "...in the prophets" (plural), letting us know he's not going to a specific writer of a specific text. Ancient authors sometimes blended texts together, especially to make plays on words to make their point.

Since Matthew never specifies, it's impossible to know which prophets and which texts. He could be referring to The Nazirite vow of devotion to God (Num. 6), or possibly to the "branch" (netser) of Isa. 11.1. Maybe both, in the sense that Matthew is taking the texts and understandings at his disposal to "fulfill" or fill up prophetic writings with his point about Jesus. Both of these are possible using the rabbinic advice named above. More likely, though, he is referring to Jer. 31.6. It's the only place in the whole OT where "nsr" (the Hebrew root of Nazarene) appears in both the MT (Masoretic text) and the LXX (Septuagint), and it's a beautiful context for Matthew's point. The chapter is about the reuniting of God with his people, telling of his love for them and the rest he will give to them. It mentions Ephraim (which he mentioned earlier, in Mt. 2.17-18), and in Jer. 6.7 it even speaks of the Lord bringing salvation to his people. It is within rabbinic exegetical parameters that Matthew can take such texts and, picking up on the wordplay of the OT source(s), bring a second, latent conceptual association of the word to the fore. We know of the typology of the Nazirite; Jesus shall be called a Nazarene—a wordplay to speak of his complete devotion to God. We know of the typology of the branch of Jesse (Isa. 11.1); Jesus shall be called a Nazarene—a wordplay that he is from the root of Jesse. We know of the prophecies of Jeremiah (31.6) about the guardians (nsr) calling people to Zion; Jesus shall be called a Nazarene—a wordplay that he is a guardian who will bring salvation to his people. If you look at the other prophecies Matthew refers to before this text (1.22-23; 2.5-6; 2.15; 2.17-18), you will see consistency in how he treats prophecy. Matthew is gathering up all these strings to tell us who Jesus is.

Let's talk about one thing the New Testament claims about Jesus being the Messiah. That is Matt 2:23. Do you see the problem? Nowhere in the Old Testament is there a prophecy saying that the Messiah will be a Nazarene. Yet the New Testament claims that it is necessary. But it's not in there. They made a mistake. The Messiah does not have to be a Nazarene. He doesn't even have to be born in Israel.