The term propitiation was used among the Greeks with reference to appease or to show mercy. It also signifies an expiation, a means whereby sin is covered and remitted. It is used in the New Testament of Christ Himself as "the propitiation", in 1 John 2:2 and 4:10, signifying that He Himself, through the expiatory sacrifice of His death, is the personal means by whom God shows mercy to the sinner who believes on Christ as the One of provided the ultimate sacrifice.
In 1 John 2:2 Christ is described as "the propitiation" for our sins, and not for ours only, but also for the sins of the whole world. The italicized "the sins of" in the King James Version gives a wrong interpretation indicating that provision is made for the whole world, so that no one is, by divine predetermination, excluded from the scope of God's mercy, on the contrary, the "propitiation" however, is made actual for only those who believe.
In John 4:10, the fact that God "sent His Son to be the propitiation for our sins" is shown to be the great expression of God's love toward man, and the reason why Christians should love one another.