The Bible's central message is atonement. From the first stories in Genesis to the last visions of Revelation it is everywhere apparent that God seeks to reconcile his people to himself and that he has provided a way to do so.
The word atonement, is almost the only theological term of English origin. It was likely first used in Tyndale's English translation as derived from the adv. phrase atonen, meaning "in accord," literally, at one.^^ In the English Bible, it is mainly used to translate the Hebrew word kipur, although it is used once in the King James New Testament to translate the Greek word katallage (see Romans 5:11). Most modern translations render this word "reconciliation" in its other occurrences throughout the N.T.
- The Work of Christ and Aspects of the Atonement (embedded audio), by Bruce Ware - Seminary lectures; part 1 starts on the topic of the atonement toward the end
Atonement in the Old Testament
Certainly the most frequently mentioned means of atonement in the Old Testament were the blood sacrifices, dominating the use of the term by constant reference in the books of Leviticus and Numbers. Atonement needed to be made for everything from heinous crimes like idolatry (Num 16:47) to mistakes of intent, when the only sin was ignorance or error, not willful disobedience (Num 15:22-29).
Day of Atonement
The Day of Atonement was an annual day of repentance for the Old Testament people of Israel the rites for which are set forth in Leviticus chapter 16 (also see Exodus 30:10; Leviticus 23:27-31, 25:9; Numbers 29:7-11). It is described as a solemn fast, a Sabbath on which no food or drink could be consumed, and on which all work was forbidden. Sacrifices were offered by the high priest as an atonement for himself and for the people.
The Bible calls the day Yom Hakippurim (Hebrew, Day of the Atonements), which the Jewish people continue to observe today as Yom Kippur.
"Perhaps the heart of the Old Testament teaching on atonement is found in Leviticus 16, where the regulations for the Day of Atonement occur. Five characteristics relating to the ritual of the Day of Atonement are worthy of note because they are generally true of atonement as it is found throughout Scripture: (1) the sovereignty of God in atonement; (2) the purpose and result of making atonement; (3) the two goats emphasize two different things, and the burning another, about the removal of sin; (4) that Aaron had to make special sacrifice for himself; (5) the comprehensive quality of the act." (Baker's Evangelical Dictionary of Biblical Theology, s.v. atonement).
Atonement in the New Testament
The New Testament presents the person and work of Christ as God's ultimate provision for atonement. The English word atonement is used to describe the New Testament concept of Christ presented as our reconciliation (2 Cor. 5:18), as a propitiation (1 John 4:10), in giving his life as "a ransom for many" (Matt. 20:28), having poured out his blood "for the forgiveness of sins" (Matt. 26:28).
"Particularly important for the full biblical picture of atonement as it is found in Christ is the sacrifice Aaron makes for himself and his family (Lev 16:11-14). Everyone, even the high priest, is guilty and needs atonement that can only be provided by God himself. The author of Hebrews emphasizes this point to make clear his doctrine of the purity of Christ as both the true and perfect sacrifice and the true and perfect priest who performs the ritual of atonement (8:3-6; 9:6-15). The Old Testament sacrifices are shown to be but shadows of the real sacrifice of Christ on the cross by the fact of Aaron's sinfulness; an imperfect high priest cannot offer a true sacrifice, just as the blood of bulls and goats could never truly pay for the offense of human sin or substitute for the shedding of human blood." (Baker's, s.v. atonement).
- Atonement from Elwell Evangelical Dictionary