Jesus Christ himself explained that he had come as a servant to give his life in an act of sacrifice for us. Thus resting on Christ's own self-interpretation, the New Testament concept of atoning redemption assumes a central role in the doctrine of atonement. In order to clarify the term atonement, we have to turn to the Old Testament. Behind the OT conception of redemption there are three basic terms and their cognates. Although all three denote different aspects of divine redemption they are all profoundly interrelated.
1)**** Kipur — Together with its cognates*kipur is applied to express the expiatory form of the act of redemption in the OT. It speaks of the barrier of sin and guilt which exists between God and humanity as being done away by the sacrifice and* propitiation made between the two factions.*Here, the subject of the atoning act is always God. Thus even though in the OT it is liturgically carried out by a high priest, the human act has to be seen as only a witness to the fact that God himself makes atonement and blots out sin by his own judicial and merciful act. Both God's judgment of wrong by offering an equivalent and the act of restoration to holiness before him are involved here in the understanding of atonement. This is brought out most clearly in the NT where we see Christ stand in as both Priest and Mediator; e.g.,*"Therefore, He had to be made like His brethren in all things, that He might become a merciful and faithful high priest in things pertaining to God, to make propitiation for the sins of the people." (Heb. 2.17).
2)**** Pedah —*Together with its*cognates pedah is applied to express the aspect of the mighty acts of God in the OT concept of redemption. Significantly these acts bring immediate deliverance from oppression of evil and out of God's judgment upon it. It also carries the notion of offering a life in substitution for another as the cost of redemption and emphasizes the dramatic nature of the redeeming act as a sheer intervention on the part of God in human affairs. When the NT writers speak of Christ in terms of victory over the tyrants--sin, death, devil, etc.--they have in view the pedah aspect of atoning redemption; e.g.,*"Since then the children share in flesh and blood, He Himself likewise also partook of the same, that through death He might render powerless him who had the power of death, that is, the devil;" (Heb*2.14).*
3)**** Go’el —*Together with its cognates go’el is used to express the aspect of someone redeeming others out of a situation of bondage or forfeited rights. The "redeemer" or go’el, upon whom the emphasis is placed in this type of redemption, possesses a bloodline kinship to those in need, and can thus claim the cause for their needs as his own and stand in for his kinsmen who cannot free or redeem themselves. This ontological concept of redemption is applied in the OT to God acting on behalf of Israel by virtue of its special covenant relationship. That covenant was, of course, fulfilled in Christ in that he stood in as go'el for Israel as Seed of Abraham and David and, by way of kinship attachment to Eve, the entire human race in recapitulation (i.e., e.g., the gathering together language of Eph. 1-2; see also Heb 2.14a --*"Since then the children share in flesh and blood, He Himself likewise also partook of the same").
See T.F. Torrance, "The Trinitarian Faith" for a full exposition of these themes.