I John 2:1-2 has been translated and re-translated through the myriad of English translations.
NIV – “My dear children, I write this to you so that you will not sin. But if anybody does sin, we have one who speaks to the Father in our defense–Jesus Christ, the Righteous One. He is the atoning sacrifice for our sins, and not only for ours, but also for the sins of the whole world.”
In the margin (v.2) the NIV has Or “…He is the one who turns aside God’s wrath, taking away our sins, and not only ours but also……”
The question is how to translate “hilasmos.”
Some translations use PROPITIATION not ATONING SACRIFICE to bring into English the Greek word hilasmos.
WIKIPEDIA (that modern source of quick research) has this definition for PROPITIATION.
In Christianity, propitiation is accomplished through Jesus Christ on the cross in his crucifixion or sacrifice, which was made possible through his sinless life. He accepted and fulfilled the wrath and indignation of God. The crucifixion or sacrifice of Christ conciliates God, who would demand a penalty for it. The concept of propitiation is associated in some Christian theological systems with indemnity, imputed righteousness, and substitutionary atonement.
Propitiation is translated from the Greek hilasterion, meaning “that which expiates or propitiates” or “the gift which procures propitiation”. The word is also used in the New Testament for the place of propitiation, the “mercy seat”. Hebrews 9:5. There is frequent similar use of hilasterion in the Septuagint, Exodus 25:18 ff. The mercy seat was sprinkled with atoning blood on the Day of Atonement (Leviticus 16:14), representing that the righteous sentence of the Law had been executed, changing a judgment seat into a mercy seat (Hebrews 9:11-15; compare with “throne of grace” in Hebrews 4:14-16; place of communion, Exodus 25:21-22).
Another Greek word, hilasmos, is used for Christ as our propitiation. 1 John 2:2; 4:10, and for “atonement” in the septuagint (Leviticus 25:9). The thought in the Old Testament sacrifices and in the New Testament fulfillment, is that Christ completely satisfied the just demands of our Holy Father for judgment on sin, by his death on the Cross of Calvary.
God, in view of the cross, is declared righteous in having been able to forgive sins in the Old Testament period, as well as in being able to justify sinners under the New Covenant (Romans 3:25,26; cf. Exodus 29:33, note). Propitiation, as hilasmos, it is satisfying the perfect justice of our Holy Father and righteous God; thereby making it possible for him to show complete mercy without compromising his righteousness or justice, i.e., mercifully covering and paying for sins, as offenses against God to turn away his wrath and to allow for, but not to include, forgiveness. This is the key to understanding limited atonement explained in 1 John 2:2 – Jesus Christ on the cross atoned for all sins of all who would believe.
Although propitiation is not a familiar word for many, the turning aside of God’s wrath and satisfying of the perfect justice of God is the issue settled at the cross.