Moses described this day (Heb. Yom Kippur) in chapter16 more fully for the priests" benefit. Here he stressed the responsibilities of the ordinary Israelite. [source][source][source]
This day was a fast rather than a feast. The people were to "humble" or "deny" themselves ( Leviticus 23:29), which involved fasting and abstaining from their normal pleasures and comforts (cf. Leviticus 16:29). God permitted no ordinary work on this day ( Leviticus 23:28; Leviticus 23:30-32). By this He taught the Israelites that the yearly removal of their sins was entirely His work, to which they contributed absolutely nothing (cf. Ephesians 2:8-9). [source][source][source]
The sacrifices the priests made on this day atoned for all the remaining sins of the believing Israelites that other sacrifices did not cover. However the benefits of the Day of Atonement lasted for only one year. [source][source][source]
"The principles taught by the Day of Atonement are valid for the New Testament believer: sin must be regularly removed in order for spiritual service and fellowship to take place. Beyond that, sin can only be removed eternally through the sacrifice of Christ made once and for all-not annually." [1][source]
Prophetically this day will find fulfillment at the second coming of Christ. Then God will purify His people who have returned to Him in repentance and self-affliction as a result of His chastening during the Tribulation period ( Zechariah 12:10; Zechariah 13:1; cf. Hebrews 9:28). [source][source][source]
"The release from the pressure of work and social inequalities, experienced on and through the Sabbath and its sister institutions, could effectively epitomize both past and future divine deliverance." [2][source]
"In order to find spiritual renewal, people must cease their works, humble themselves before God, and draw near to him on the merits of the atoning sacrifice." [3][source]