"... As the idea of the ascent to heaven develops in apocalyptic and Merkabah literature, the concentric ring of courts becomes the levels or palaces separating the celestial from the mundane. In his study of the priestly investiture of Levi in heaven in the Greek Testament of Levi, Benedikt Otzen shows how the hierarchy of the angels in the levels of heaven leading up to the throne of God reflects the hierarchy of priests and Israelites in the temple in Jerusalem and the courts in which they served or to which they had access. As Philip Alexander describes the concept in 3 Enoch, God’s throne “is located in the seventh heaven, in the middle of seven concentric palaces or temples, and can be approached only through seven doors guarded by fierce guardian angels.” The wall of flame through which Enoch must enter the precincts of the celestial temple in 1 Enoch 14:10 seems to function in a similar manner by establishing a court to serve as a buffer to anything that is mundane, and as the sage penetrates further into the celestial temple he reaches a place off limits even to the angelic priests who stand before the Deity and faces an implied question as a mortal about the legitimacy of his own presence in the celestial courts (1 Enoch 15:2) ..."

Suter, David W. "Temples and the Temple in the Early Enoch Tradition: Memory, Vision, and Expectation" in Boccaccini, Gabriele, and John J. Collins (eds.) The Early Enoch Literature (pp. 195-218) Brill, 2007