Hebrews 10 sums it up...

It's a good idea to read Leviticus 16 and it's context before studying Hebrews 10. Several years ago I worked for a Christian school and had the opportunity to do a series of chapels on the different sacrifices under the Old Covenant, as well as the amazing layout and function of the Tabernacle. The traditions God started with the Hebrew people are astounding and very interesting. Read through and pause to take in the scenes and the amazing details. Understanding the roll of sacrifice and blood in the Old Testament is essential to one's comprehension of Christ's sacrifice once for all.

Christ's Sacrifice Once for All
    1 The law is only a shadow* of the good things* that are coming-not the realities themselves.* For this reason it can never, by the same sacrifices repeated endlessly year after year, make perfect* those who draw near to worship.* 2 If it could, would they not have stopped being offered? For the worshipers would have been cleansed once for all, and would no longer have felt guilty for their sins.* 3 But those sacrifices are an annual reminder of sins,* 4 because it is impossible for the blood of bulls and goats* to take away sins.*
    5 Therefore, when Christ came into the world,* he said: "Sacrifice and offering you did not desire, but a body you prepared for me;*
    6 with burnt offerings and sin offerings you were not pleased.
    7 Then I said, 'Here I am-it is written about me in the scroll* - I have come to do your will, O God.' "* *
    8 First he said, "Sacrifices and offerings, burnt offerings and sin offerings you did not desire, nor were you pleased with them"* (although the law required them to be made). 9 Then he said, "Here I am, I have come to do your will."* He sets aside the first to establish the second. 10 And by that will, we have been made holy* through the sacrifice of the body* of Jesus Christ once for all.*
    11 Day after day every priest stands and performs his religious duties; again and again he offers the same sacrifices,* which can never take away sins.* 12 But when this priest had offered for all time one sacrifice for sins,* he sat down at the right hand of God.* 13 Since that time he waits for his enemies to be made his footstool,* 14 because by one sacrifice he has made perfect* forever those who are being made holy.*
    15 The Holy Spirit also testifies* to us about this. First he says:
    16 "This is the covenant I will make with them after that time, says the Lord. I will put my laws in their hearts, and I will write them on their minds."* *
    17 Then he adds: "Their sins and lawless acts I will remember no more."* *
    18 And where these have been forgiven, there is no longer any sacrifice for sin.