“The Son of God who made us was made one of us, and He rules us as our king because as our creator He made us.
He through whom we are ruled is none other than He through whom we were made, and we are called Christians because He is the Christ.
The title ‘Christ’ is derived from chrism, which is used in anointing. Kings and priests used to be anointed, and Christ was anointed as both king and priest.
As king He fought for us, and as priest He offered Himself for us.
When he fought for us He was to all appearances overcome, but in truth He was the victor. He was crucified, and from the cross to which He was fastened He slew the devil, and thus He proved Himself our king.
But in what sense is he a priest? Because he offered himself for us.
Give your priest something He can offer. But what could human beings have found that would serve as a clean victim?
What shall your victim be? What clean sacrifice can a sinner offer? Wicked, impious pretender, whatever you bring is tainted, yet something clean is needed to be offered for you.
Look for something fit within yourself: you will find nothing.
Look among your possessions for an acceptable offering: but God takes no pleasure in rams or he-goats or bulls. They all belong to Him anyway, even if you do not offer them.
Go on, then, offer him a clean sacrifice. But you are a sinner, a wicked person, and your conscience is defiled.
If you were purified first you would, perhaps, be in a position to make a clean offering, but, if you are to be purified, something must be offered on your behalf.
What are you going to offer for yourself, to effect your cleansing? Only if you have first been cleansed will you be able to offer anything clean.
Let a clean priest offer Himself, then, and cleanse you. That is what Christ did.
He found nothing clean in human beings that He could offer on behalf of human beings, so He offered Himself as a clean victim.
How auspicious a victim, how genuine; and how spotless a sacrifice!
What He offered was not something we had given Him; rather did He offer what He took from us, but He offered it in a clean condition.
He took flesh from us, and that was what He offered, but whence did He take it?
From the womb of His virgin mother, so that He might offer it clean for us who were unclean.
He is our king and He is our priest.
Let us rejoice in Him.”
–Saint Augustine, Expositions of the Psalms 121–150, ed. Boniface Ramsey, trans. Maria Boulding, vol. 20, The Works of Saint Augustine: A Translation for the 21st Century (Hyde Park, NY: New City Press, 2000), 20: 584–585. Augustine is riffing on Psalm 149:2.