What does Hebrews 9:20 mean?

This is part of a reminder that even the old covenant was "inaugurated," or begun, with an understanding of the importance of a blood sacrifice. Verse 18 began this reference, which speaks of the time when Moses first brought the commands of God to the people. Then, Moses used sacrificial blood in something like a dedication ceremony. Blood would be a central part of the old covenant, as repeated animal sacrifice was necessary to temporarily cover the sins of the people. This, of course, is a limited and flawed system. God's ultimate intent was not to continue this way; rather, the old covenant was meant to be symbolic of the new covenant.

In Exodus 24:6–8, Moses indicates that the use of blood was meant to introduce this covenant to the people of Israel. During the Last Supper, Jesus used similar language when instituting the new covenant (Matthew 26:28). This verse is part of a developing idea, completed in verse 22: that blood is a necessary component of forgiveness. That leads into a discussion of why, and how, Jesus' sacrifice was not only necessary, but can completely accomplish our salvation.