Our advocate is at the same time the propitiation for our sins, and this perfectly equips him to do his work of advocacy. As our propitiation he appeases the holy anger of God towards sinners by becoming our substitute and bearing the punishment that we deserve.
The knowledge that Christ has taken in full the punishment for our sins makes us able to approach God without fear.
Those who regard the atonement as unnecessary, and think that God would be arbitrary or spiteful in requiring sin to be punished before he can forgive it, do not understand the antagonism between God’s nature and sin, and probably feel little antagonism to sin from their own nature.
There is not a single person in the world who is without sin; all are in need of this atonement.
Christ did not come to save all human beings but only his sheep (John 10:11, 26; John 17:9), the elect, chosen from before the foundation of the world (Ephesians 1:4). Why then does John say that the Lord is the propitiation for the sins of the whole world? Not to teach that he died for every individual in the world, but that there is no other atonement available to anyone apart from that provided by Christ, and to show believers that they have no other way of approaching God than that available to all mankind in general. The Jews in particular needed to hear this because they were convinced that God would deal only with their nation, but by this statement John includes the Gentiles also.