It is a priest’s duty to offer something, and, according to the Law, to enter into the Holy places by means of blood; seeing, the, that God rejected the blood of bulls and goats, this high Priest (Jesus) was indeed bound to make passage and entry into the holy of holies in heaven through His own blood, in order that He might be the everlasting propitiation for our sins. Priest and victim, then, are one; the priesthood and sacrifice are, however, exercised under the conditions of humanity. For he was led as a lamb to the slaughter, and he is a priest after the order of Melchizedech. (On the Christian Life, St Ambrose, CA 370 AD)
Outside of Jesus Christ, there has never been a priest who was able to be the one who offers and at the same time be the offering; for if there were such a priest, he would only make one offering. None but Jesus could rise from the dead, and remain a priest forever. Therefore, every priest before Jesus was a type (foreshadow) of Him, and every priest after Jesus is an icon (image) of the one, true, high priest. Both serve as bridges that lead others to the one who St Ambrose calls the everlasting propitiation for our sins. To be “a propitiation,” means to be a kind of satisfaction or offering that obtains atonement. In other words, the point of the offering is “atonement.” The word atonement is a conjunction of three words, at-one-ment. It is the title given to the event wherein one person is made one with another person. Our high priest made such an offering in his own physical person that it produced at-one-ment between man and God. This is what he refers to when he says that by this offering He made passage and entry into the holy of holies in heaven through His own blood. Ambrose is explaining that salvation is a life procured for us by Jesus that is lived out within the holy of holies, and therefore salvation is nothing less that living con-joined to God. Salvation is the divinization of sinful humans by the grace of Christ’s offering for us. Salvation= propitiation + atonement + divinization. It is this task that our great high priest Jesus Christ has accomplished once and for all. Every priest since Jesus has merely presented Christ to the people of God, and escorted them down the path that was opened into the heavenlies by the true high priest.