Expiation is used once in the New American Standard Bible (Numbers 35:33) and eight times in the Revised Standard Version. It is used to translate two Hebrew words in the Old Testament which are usually translated purification, atonement, or cleansing (such as in the ESV), and three variations on the Greek word hilasterion in the New Testament, again usually translated atonement or propitiation. Some Bible scholars and theologians have argued very strongly that the New Testament translations should only use "propitiation" to translate "hilasterion", but this is a technical issue beyond the scope of this article.
What is the meaning of expiation?
The word "expiation" when applied in the Bible means to bear the sin of another, and in the New Testament in particular, Jesus' act of bearing our sin for us on the Cross. The reason most translations do not use the term is that it does not have a wide enough meaning to translate most of the words the RSV uses it for, especially the Greek hilasterion. Expiation actually carries a meaning that is communicated as part of the concept of atonement, which is why many prefer "atonement" and "expiation" has been abandoned by most translations.
How is Jesus' sacrifice propitiation for our sins?
What is the meaning of substitutionary atonement?
How is Jesus a ransom for many? What is ransom theory?
What is the meaning of Romans 6:23, "the wages of sin is death"?
Why did Jesus have to die?
Truth about Salvation