The most solemn holy day on the Jewish calendar is Yom Kippur (‘Day of Covering’), or The Day of Atonement.
The word ‘atonement’… means ‘a making at one’, and points to a process of bringing those who are estranged into a unity. 
The Day of Atonement was a day for the people to fast (‘afflict yourselves’) and abstain from working. The Day served as a mournful reminder to the people that their sins separated them from God and that the only thing that could make them ‘at one’ with God was the High Priest offering a yearly substitute sacrifice whose blood would cover their sins. Everything involved in the Day of Atonement served as an imperfect model of the perfect ministry of Christ. We are told the High Priest served “…a copy and shadow of the heavenly things.” (Heb. 8:5, ESV) This is evident in the Old Testament because the models themselves had to be first atoned for by sacrifices. Even the offerings themselves were imperfect. “But in these sacrifices there is a reminder of sins every year. For it is impossible for the blood of bulls and goats to take away sins.” (Heb. 10:3–4, ESV) Hebrews makes this clearer.
|The Shadow||Atonement||The Heavenly Thing|
|The Tabernacle||Lev.16.16,20||God’s Presence (Heb. 9.24)|
|The Priest||Lev.16.6,11||Jesus (Heb.4.14; 9.11)|
|The Animal Sacrifice||Jesus’ body (Heb. 9.12; 10.10)|
|The People||Lev.16.15||Heb. 10.14|
Jesus Christ was the perfect High Priest who took a perfect offering (Himself) into the very presence of God and made a complete atonement for the people so that they could be perfected forever. “For by a single offering he has perfected for all time those who are being sanctified.” (Hebrews 10:14, ESV)
A yearly offering instituted a multitude of years before the time of Jesus’ sojourn on Earth, the Day of Atonement foreshadowed the sacrifice of Christ for our sins. What confirmation of God’s word and plan of salvation!
The Day of Atonement pictures the greatest work of Jesus Christ, the giving of Himself to God as our sin offering!
Further reading: Lev. 23:26-32; Lev. 16; Heb. 9:1-10:39; Rom. 3:23-25
 L. L. Morris, “Atonement,” ed. D. R. W. Wood et al., New Bible Dictionary (Leicester, England; Downers Grove, IL: InterVarsity Press, 1996), 102.