"...Jesus' death on the cross is not the place or the primary means of atonement for the author of Hebrews. Rather, when the writer claims in 8:4 that Jesus can only serve as a high priest in heaven, he intends to say that the great redemptive moment of the Christ event occurred not when Jesus was crucified, but after he was resurrected and ascended into heaven. There he presented himself alive and incorruptible before God. Just as Yom Kippur [the Day of Atonement] does not focus on the slaughter of the victim, but the presentation of its blood--that is, its life--before God, so also the author of Hebrews thinks in terms of the presentation of Jesus' indestructible life before God as the central act that effects the atonement."1
Read the rest of this interesting article here, starting at page 211.
1 David M. Moffitt, "Blood, Life, and Atonement: Reassessing Hebrews' Christological Appropriation of Yom Kippur," in The Day of Atonement: Its Interpretations in Early Jewish and Christian Traditions, ed. Thomas Hieke and Tobias Nicklas (Leiden, The Netherlands: Koninklijke Brill, 2012), 211-212