The Day of Atonement involves not only the forgiveness of sin; it pictures the removal of the primary cause of sin, Satan. It teaches us that Jesus Christ gave His life to atone for the sins of all mankind. It also points to the time when Satan will be bound for 1,000 years (Leviticus 16:29-30, Leviticus 16:20-22; Revelation 20:1-3). This Holy Day pictures our High Priest, Jesus Christ, making atonement for our sins, which allows us to be reconciled to God and enter into the "holiest of all" (Hebrews 9:8-14; Hebrews 10:19-20). By fasting on this day, we draw closer to God and picture the reconciliation of mankind to God. Christ is essential in this process as our High Priest (Hebrews 4:14-15; Hebrews 5:4-5, Hebrews 5:10) and as our eternal sacrifice for sin (Hebrews 9:26-28).

To read more about the Day of Atonement click the links below. 

https://www.ucg.org/tags/atonement

Atonement: Removal of Sin's Cause and Reconciliation to God

The Binding of Satan Pictured on the Day of Atonement