What does Hebrews 9:18 mean?

This passage of Scripture explains how the physical aspects of the old covenant were meant as symbols of the new covenant. The limitations of the temple, priests, and sacrifices were all intended to point towards God's ultimate, final plan. As told by God in His Word, this new covenant would be eternal and perfect, rather than temporary and limited. Leading up to this verse, the writer of Hebrews pointed out that the blood of animals could only accomplish limited atonement for sin. That did not make animal sacrifices worthless, but it did mean that the sacrifice of Jesus Christ, who was fully human, can achieve what prior shedding of blood could not.

Verses 18 through 20 remind the readers of how the very beginning of the old covenant involved bloodshed. These verses refer to incidents described in Exodus chapter 24, where Moses sprinkles sacrificial blood in order to "inaugurate" the covenant between God and Israel (Exodus 24:6–8).