Therefore he had to be made like his brothers in every respect, so that he might become a merciful and faithful high priest in the service of God, to make propitiation for the sins of the people. (Heb 2.17, ESV)

We do not use the word propitiate very much in the English language anymore so it behooves us to understand what it means (and what the underlying Greek word means). The Holman Treasury of Key Bible Words [HTKB] has an excellent article on propitiation.

It comments: “In ancient times, many polytheists thought of their gods as unpredictable beings, liable to become angry with their worshipers for any trifle. When any misfortune occurred, it was believed that a god was angry and was therefore punishing his worshipers. The remedy was to offer the god a sacrifice to appease his anger. This process was called ‘propitiation.'”

Propititation then means to appease someone’s wrath and used in the Bible it means to appease God’s wrath against sin. However: “The Greek term for “propitiation,” hilasmos, occurs in some important passages: Romans 3:25; Hebrews 2:17; 1 John 2:2; 4:10. The message we get from these passages is that propitiation (also called “expiation”) pertains to Christ’s sacrifice for sins in order to bring about a peaceful relationship between God and humanity.” [HTKB]

We err if we assume that God’s wrath is like our human wrath:

“His anger is not an irrational lack of self-control, as it so often is with humans. His anger is the settled opposition of His holy nature to everything that is evil.” [HTKB]

When Jesus propitiated or appeased God’s wrath against sin at the cross, he was paying the punishment that is due because of sin and in light of God’s nature which is to oppose evil at all times, in every place, in all things. For this I am grateful because I do understand [to some degree] the evil that lurks in my own heart.

Leave it to the Apostle John to summarize the truth of propitiation in a way that we understand:

“In this is love, not that we have loved God but that he loved us and sent his Son to be the propitiation for our sins.” (1 John 4.10)