My view of the origin of Christianity begins with the assumption that it started in pre-70 CE Judea. So I like to look for its roots in sources that come from pre-70 CE Judea, especially the Dead Sea Scrolls.
The Damascus Document, for example, refers to a singular Messiah and identifies its sect as "the way" that practiced "the new covenant" in a place called "Damascus," so this catches my attention because these are terms that are used in Christian writings to describe early Christians.
Concerning "the way," Bauckham says in "The Dead Sea Scrolls as Background to Postbiblical Judaism and Early Christianity" (pg. 78):
"Although the Qumran community and the early Christians were certainly not the only Jews to focus their hopes on the Isaianic picture of the way ... *they are the only two groups we know to have applied the image of this way to their own way of life*."
Examples of "the way" and "the new covenant" and "Damascus" in the Damsacus Document are:
"they were like blind men groping for the way."
"He raised for them a Teacher of Righteousness to guide them in the way of His heart."
"the way of God."
"those who departed from the way."
"He led them astray in a wilderness without way."
"the New Covenant in the land of Damascus."
"the New Covenant, which they made in the land of Damascus."
These terms are also used to describe early Christianity in Acts:
"But Saul, yet breathing threatening and slaughter against the disciples of the Lord, went unto the high priest, and asked of him letters to Damascus unto the synagogues, that if he found any that were of the Way, whether men or women, he might bring them bound to Jerusalem."
"they ... expounded unto him the way of God more accurately."
"And about that time there arose no small stir concerning the Way."
"I persecuted this Way unto the death, binding and delivering into prisons both men and women. As also the high priest doth bear me witness, and all the estate of the elders: from whom also I received letters unto the brethren, and journeyed to Damascus to bring them also that were there unto Jerusalem in bonds to be punished."
"the Way, which they call a sect."
The examples of "Damascus" in Paul are:
"I did not go up to Jerusalem to see those who were apostles before I was, but I went into Arabia. Later I returned to Damascus" (Gal. 1:17).
What he means by "Damascus" here is debatable (whether the city or the general region like in the Damascus Document and 1 Kings 19:15, "And the Lord said to him, 'Go, return on your way to the wilderness of Damascus. And when you arrive, you shall anoint Hazael to be king over Syria'"), but he mentions it along with the general region of Arabia, and elsewhere he distinguishes "Damascus" from the city of Damascus:
"In Damascus the governor under King Aretas had the city of the Damascenes guarded in order to arrest me" (2 Cor. 11:32):
Paul is also aware of the idea of a "new covenant":
"He has made us competent as ministers of a new covenant" (2 Cor. 3:6).
"This cup is the new covenant in my blood" (1 Cor. 11:25).
The Damascus Document also gives a brief history of the sect that says that God had “visited [or "he turned attention to"] them, and He caused a root of planting to spring forth from Israel and Aaron.”
While I see the "root of planting" (shoresh mattat) that sprang forth "from Israel and Aaron" as a reference to the founding of the sect and not to an individual (cf. 1QS col. 8: "When these are in Israel, the Council of the Community shall be established in truth. It shall be an Everlasting Plantation, a House of Holiness for Israel, an Assembly of Supreme Holiness for Aaron"), Campbell notes on pg. 54 of “The Use of Scripture in the Damascus Document”:
“[A]ny link between the formation of the 'remnant' and the 'root' is not explicated [in the Damascus Document], although the emergence of the [Righteous Teacher] is clearly placed twenty years after the foundation of the 'root.'"
The word “root” (shoresh) here is singular and tied to the expression "from Israel and Aaron" that the Damascus Document uses elsewhere in its description of a singular Messiah, as Wacholder notes on pg. 214 in "The New Damascus Document":
https://books.google.com/books?id=ZZ58U ... nt&f=false
And Blanton notes on pg. 51 of "Constructing a New Covenant: Discursive Strategies in the Damascus Document" that this connecting phrase "resonates with the sect's messianism":
https://books.google.com/books?id=rdaTp ... ah&f=false
So both the "root" and "the Messiah" are singular in the Damascus Document and connected to the phrase "from Aaron and Israel" (or "from Israel and Aaron), and "root" imagery is used to describe both the Messiah and the Suffering Servant in the OT:
“In that day, the Root of Jesse will stand as a banner for the peoples” (Is. 11:10).
http://biblehub.com/interlinear/isaiah/11-10.htm
"He grew up before him like a tender shoot, and like a root out of dry ground."
http://biblehub.com/interlinear/isaiah/53-2.htm
And "root" and "plant" imagery is also used to describe Jesus in Christian writings:
"Isaiah says, ‘The Root of Jesse will spring up'” (Rom. 15:12).
“I am the Root and the offspring of David” (Rev. 22:16).
“The Root of David” (Rev. 5:5).
“Beliar … will persecute the plant which the Twelve Apostles of the Beloved have planted” (Ascension of Isaiah 4:2-3).
So “root” is not only used to describe the Messiah in the OT and Jesus in Christian writings, whatever it may mean in the Damascus Document has something to do with God having “visited” (or turned his attention to) a remnant of Israel and causing it to happen twenty years before the rise of the Teacher of Righteousness (even though I lean towards the idea that the root refers to the sect).
The Damascus Document also mentions “the fallen tent of David” of Amos 9:11 (which is applied to Jesus in Acts 15:16), and “strike the shepherd” of Zech. 13:7 (which is applied to Jesus in Mk. 14:27), and “the fountain of living waters” of Zech. 14:8 and Jer. 2:13 (which is applied to Jesus in Rev. 7:17).
Because of these kinds of correspondences, for me a place to look for the "root" of post-70 CE Jesus is in the Damascus Document, which expects that "they shall see His salvation [yeshuato in Hebrew, i.e., His "yeshua"] because they took refuge in His holy Name" in the Messianic Age.
You know in spite of all you gained, you still have to stand out in the pouring rain.