Well known passages from Heb treat the blood of Christ as both that of a “Testament” and that of a sacrifice of atonement. The first corresponds to the Pentecost while the second to the Day of Atonement. This is even stranger given that Jesus was actually crucified as a lamb on the Passover. Three OT feasts are here joined as unified typos of the death of Christ. How is it possible? R. Murray (1999) explains a pre-Christian tradition underlying Heb 4:1-12 by a pre-Christian Palestinian Aramaic Targum to Joshua 5 published in 1991 by H. Fahr and U. Glessmer. Indeed, this tradition, not less important also in the early Christianity, could explain why, according to the example of Joshua, the feasts of Passover and of “Entering into the Covenant” could become united (cf. also W. H. Brownlee 1982 on 1QS). As to the Day of Atonement, its presence becomes clear from Heb 9 where the sense of the word “testament” is strongly connected to the death: “For where a testament is, there must of necessity be the death of him that made it” (9:16). This is alluding to both deaths of Christ and of Moses, and so, the beginning of the OT is postponed until the time of Joshua’s crossing of Jordan — in a perfect conformity with the above mentioned Targumic tradition. The calendar where the three basic feasts with Jewish background became unified is known from various pre-Christian and early Christian sources and in various modifications. It is the 364-day calendar containing seven cycles of seven weeks each year where the end of each seven week cycle was an important feast. One its modification that is important for our purpose is implied in ShirShab, and probably all Christian calendars still have various imprints of it.
Another series of OT references (esp. Heb 9:8 sqq) leads us to consider the liturgical placement of the community of the “Hebrews” as a new Holy of Holies that was prefigured by that of the Tabernacle of Moses. This, in turn, leads us to the Passover rites of the Book of Jubilees and the Gospels (Jaubert 1972).
Davidic and Zion references lead us to the Zion traditions belonging to the “Jewish matrix” of Christianity, such as those of Vitae Prophetarum and Inscription on the Chalice of Solomon, and, finally, to historical Zion. The Christians were always venerating Zion as a holy place of David, being indifferent to the Temple Mount. Moreover, the earliest Christian church on Zion under Emperor Hadrian (early 2nd cent.) is depicted as “seven synagogues”. This sevenfold structure of the Zion sanctuary was preserved even in the early Byzantine Zion basilica (394). This is the moment to recall seven “sanctuaries” in ShirShab.
“Hebrews” must be the Christian community inheriting pre-Christian Zion that was already alternative to the Temple.