In Lewis Sperry Chafer's Systematic Theology, he notes some of the complexities concerning the doctrine of atonement.

In the Old Testament

The word "atonement" is found in the Scriptures only in the Old Testament (in English translations), except where Romans 5:2 is incorrectly translated. In Romans 5:2, it is a translation of two Hebrew words, and one of them, "kiiphar," is used about seventy times in the Scriptures. Its meaning is "to cover." This distinct and limited meaning of the Hebrew word should not be interpreted with New Testament ideas, which contemplate a finished or completed work. In the Old Testament, the one who had sinned was himself fully forgiven and released, but its basis was only typical--not actual. God forgave and restored where sin was only covered by animal sacrifices, but the true basis upon which forgiveness could ever be granted was the intention on God's part to later deal with the sin that He had forgiven; i.e., righteously and effectively through the sacrificial death of His Son on the cross. That efficacious death was a type of the required animal sacrifice. Romans 3:25 says, "God presented Christ as a sacrifice of atonement, through the shedding of his blood--to be received by faith. He did this to demonstrate his righteousness, because in his forbearance he had left the sins committed beforehand unpunished."

Christ bore the sins which were committed before, and these sins had already been forgiven on the typical ground that they were covered. This is one of the major accomplishments of Christ's death. It is as though unnumbered promissory notes had been handed to Christ for Him to pay. If the notes are paid as promised, God is proved to have been righteous in the forgiving of sin with no other demands having been made upon the sinner than that an offering be brought which, regardless of how much it was understood by that sinner, was in God's sight an anticipation and recognition of His final meeting of every holy demand against sin by the efficacious blood of Christ. In other words, God passed over the sins, not judging them finally at the time they were forgiven. Such a course, it is obvious, would be a very unrighteous dealing if those sins were not in due time to be brought into judgment. All sins of the Mosaic age were thus shown to have been "covered" but not "taken away." In contrast to this temporary expedient, all sin which God forgives has been and is now "taken away."

This vital contrast appears in two New Testament passages. Hebrews 10:4, 11-14 says, "It is impossible for the blood of bulls and goats to take away sins... Day after day every priest stands and performs his religious duties; again and again he offers the same sacrifices, which can never take away sins. But when this priest had offered for all time one sacrifice for sins, he sat down at the right hand of God, and since that time he waits for his enemies to be made his footstool. For by one sacrifice he has made perfect forever those who are being made holy."

John 1: 29, "Look, the Lamb of God, who takes away the sin of the world!" This great declaration from John was a doctrinal innovation of immeasurable proportions. The same contrast between the divine dealings with sin in the past dispensation and in the present dispensation is indicated again at Acts 17:30, which says, "In the past God overlooked such ignorance, but now he commands all people everywhere to repent."

In the New Testament

The word "atonement" is not really found in the New Testament, although some English translations incorrectly translate the word in Romans 5:11 as "atonement." The meaning of atonement is "at-one-ment"; those once estranged are brought into agreement. The New Testament word for this is reconciliation. The word "atonement" as such is confined to the old order and is not used by the Holy Spirit respecting any feature of the new order in Christianity.

In Theology

Modern theologians use the word "atonement" as a term to represent all that Christ did on the cross. In Chafer's Systematic Theology, he explains fourteen great achievements by Christ in His death on the cross. These achievements reach beyond all present time into other ages, and past human situations into angelic spheres. It is not possible for a single word to express all that Christ's death on the cross accomplished. This is especially true for the word "atonement" since it doesn't even appear in the New Testament, and it is used in the Old Testament to represent one idea that is completely foreign to and superseded in the New Testament.

This discussion may be summarized with a quote from an article on atonement in the International Standard Bible Encyclopedia:

In the English New Testament the word "atonement" is found only at Romans 5: 11 and the American Revised Version changes this to "reconciliation." While in strict etymology this word need signify only the active or conscious exercise of unity of life or harmony of relations, the causative idea probably belongs to the original use of the term, as it certainly is present in all current Christian use of the term. As employed in Christian theology, both practical and technical, the term includes with more or less distinctness: the fact of union with God, and this always looked upon as a broken union to be restored or an ideal union to be realized, the procuring cause of atonement, variously defined, the crucial act wherein the union is effected, the work of God and the response of the soul in which the union becomes actual. Inasmuch as the reconciliation between man and God is always conceived of as effected through Jesus Christ (2 Cor. 5:18-21) the expression, "the Atonement of Christ," is one of the most frequent in Christian theology. Questions and controversies have turned mainly on the procuring cause of atonement, above, and at this point have arisen the various "theories of the Atonement."

Owen Weber 2012