Word Study - Propitiation

Now all these things are from God, who reconciled us to Himself through Christ and gave us the ministry of reconciliation.  2 Corinthians 5:18

Propitiation

See Atonement

that by which God is rendered propitious, i.e., by which it becomes consistent with his character and government to pardon and bless the sinner. The propitiation does not procure his love or make him loving; it only renders it consistent for him to execise his love towards sinners.

In Romans 3:25 and Hebrews 9:5 (A.V., "mercy-seat") the Greek word hilasterion is used. It is the word employed by the LXX. translators in Exodus 25:17 and elsewhere as the equivalent for the Hebrew kapporeth , w
hich means "covering," and is used of the lid of the ark of the covenant ( Exodus 25:21 ; 30:6 ). This Greek word (hilasterion) came to denote not only the mercy-seat or lid of the ark, but also propitation or reconciliation by blood. On the great day of atonement the high priest carried the blood of the sacrifice he offered for all the people within the veil and sprinkled with it the "mercy-seat," and so made propitiation.

In 1 John 2:2 ; 4:10 , Christ is called the "propitiation for our sins." Here a different Greek word is used (hilasmos). Christ is "the propitiation," because by his becoming our substitute and assuming our obligations he expiated our guilt, covered it, by the vicarious punishment which he endured. (Compare Hebrews 2:17 , where the expression "make reconciliation" of the A.V. is more correctly in the RSV "make propitiation.")

Covering; atoning sacrifice.

My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous: and he is the PROPITIATION for our sins: and not for ours only, but also for the sins of the whole world. ( 1 John 2:1 Isaiah 2:1-2 )

Theological Implication:

The basal idea in Hebrew terms is that of covering what is offensive, so restoring friendship, or causing to be kindly disposed. The Greek terms lack the physical reference to covering but introduce the idea of friendliness where antagonism would be natural; hence, graciousness. Naturally, therefore, the idea of expiation entered into the concept. It is especially to be noted that all provisions for this friendly relation as between God and offending man find their initiation and provision in God and are under His direction, but involve the active response of man. All heathen and unworthy conceptions are removed from the Christian notion of propitiation by the fact that God Himself proposed, or "set forth," Christ as the "mercy-seat," and that this is the supreme expression of ultimate love. God had all the while been merciful, friendly, "passing over" man's sins with no apparently adequate, or just, ground for doing so. Now in the blood of Christ sin is condemned and expiated, and God is able to establish and maintain His character for righteousness, while He continues and extends His dealing in gracious love with sinners who exercise faith in Jesus. The propitiation originates with God, not to appease Himself, but to justify Himself in His uniform kindness to men deserving harshness. Compare also as to reconciliation, as in Romans 5:1-11; 2 Corinthians 5:18.

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For Further Study

What is Propitiation? Bible Meaning and Definition (biblestudytools.com)

Propitiation - Encyclopedia of The Bible - Bible Gateway

What Does “Propitiation” Mean? Biblical Meaning & Understanding (christianity.com)