Propitiation is the act of appeasing or making well-disposed a deity, thus incurring divine favor or avoiding divine retribution. While some use the term interchangeably with expiation, others draw a sharp distinction between the two. The discussion here encompasses usage only in the Christian tradition.
In Romans 3:25 the King James Version, New King James Version, New American Standard Bible, and the English Standard Version translates "propitiation" from the Greek word hilasterion. Concretely it specifically means the lid of The Ark of The Covenant. The only other occurrence of hilasterion in the NT is in Hebrews 9:5, where it is translated as "mercy seat" in all of the Bible translations named above as well as the Revised Standard Version and the New Revised Standard Version.
For many Christians it has the meaning of "that which expiates or propitiates" or "the gift which procures propitiation". (KJV) reads: "And he is the propitiation for our sins: and not for ours only, but also for the sins of the whole world." There is frequent similar use of hilasterion in the Septuagint, ff. The mercy seat was sprinkled with blood on Yom Kippur (), representing that the righteous sentence of the Law had been executed, changing a judgment seat into a mercy seat (; compare with "throne of grace" in ; place of communion, ().
Another Greek word, hilasmos, is used for Christ as our propitiation in 1 John 2:2; 4:10; and in the Septuagint (; ; ). The thought in the OT sacrifices and in the NT fulfillment, is that Christ completely satisfied the just demands of the Holy Father for judgment on sin, by his death at Calvary (). TDNT, however, takes a different view of Hebrews: "If the author uses the ritual as a means to portray Christ's work, he also finds that in the new covenant the literal offerings of the ritual are replaced by the obedience of Christ (10:5ff.; cf. Ps. 40) and the Christian ministry of praise and mutual service (13:15-16; cf. Ps. 50). In other words, total self-giving, first that of Christ, and then, on this basis, that of his people, is the true meaning of sacrifice.