These verses also contain instructions for the yearly celebration of the Day of Atonement. The fact that the Israelites repeated it year by year points to the non-finality of the atonement that animal sacrifices made (cf. Hebrews 9:7-12). [source][source][source]
All the Israelites were to humble their souls (fast and repent) and refrain from work in preparation for this event. This self-affliction included spiritual humbling as well as going without food (cf. Isaiah 58:3). Fasting was an indication that the practitioner regarded his need to seek God as more pressing than his need to eat. It often accompanied prayer (cf. Psalm 35:13). Refraining from work resulted from the same sense of priority. No human activity was necessary nor did God permit it in addition to the sacrifice that He provided to atone for sin. [source][source][source]
The promise of God in Leviticus 16:30 is one that the Israelite was to believe and by which he could enjoy assurance of his fellowship with God. It is very clear from this verse and similar statements (cf. Leviticus 16:16; Leviticus 16:22) that God promised forgiveness and cleansing to all who trusted in the efficacy of the sacrifices that He provided and prescribed. [1][source]
The writer of the Book of Hebrews saw the Day of Atonement as prefiguring Jesus" crucifixion ( Hebrews 9). Though the Day of Atonement is not something Christians observe, we can learn the nature of sin, the need for atonement, and the superiority of Christ"s sacrifice by reflecting on this Jewish ritual in the light of Calvary (cf. Hebrews 10:22-25). Some Christians practice self-affliction during Lent for essentially the same reason the Israelites afflicted themselves before the Day of Atonement. [source][source][source]
"The only way of access into the presence of the LORD is by the application of the atoning blood on the mercy seat and the removal of the sins of the penitent by placing them on a scapegoat." [2][source]
After the Romans destroyed the Jerusalem temple in A.D70 , the rabbis wanted to preserve the rituals of the Day of Atonement for future generations. They could not, of course, continue to practice Yom Kippur as the Mosaic Law specified without the temple. So they substituted prayer, repentance, and giving to charity for sacrifices and rituals that they could no longer practice. They also preserved the descriptions of the former rituals of Yom Kippur (now called the Avodah) in the mahtzor (the special prayer book used on Yom Kippur). [source][source][source]