Article 1. Whether it is fitting that Christ should be a priest?
“The Lord showed me the high-priest standing before the angel of the Lord. (Zechariah 3:1)” It seems that to be a priest is to be less than an angel. However, “We have therefore a great high-priest that hath passed into the heavens, Jesus, the Son of God. (Hebrews 4:14)”
The office of a priest is to be a mediator between God and the people. “Every high-priest taken from among men is ordained for men in the things that appertain to God, that he may offer up gifts and sacrifices for sins.” Christ does exactly this in the perfect and only truly efficacious way.
“Wherefore, as to others, one is a lawgiver, another is a priest, another is a king; but all these concur in Christ, as the fount of all grace. Hence it is written (Isaiah 33:22): The Lord is our Judge, the Lord is our law-giver, the Lord is our King: He will come and save us.”
Article 2. Whether Christ was Himself both priest and victim?
It is the duty of the priest to slay the victim. Christ did not slay Himself, but of His own free-will He exposed Himself to death, according to Isaiah 53:7: “He was offered because it was His own will.” Thus He is said to have offered Himself.
Man is required to offer sacrifice for three reasons. For the remission of sin, that he may be preserved in a state of grace, and in order that his spirit be perfectly united to God. All these effects were conferred on us by the humanity of Christ. Therefore Christ Himself, as man, was not only priest, but also a perfect victim, being at the same time victim for sin, victim for a peace-offering, and a holocaust.
Article 3. Whether the effect of Christ’s priesthood is the expiation of sins?
The blood of Christ, Who by the Holy Ghost offered Himself unspotted unto God, shall cleanse our conscience from dead works, to serve the living God. (Hebrews 9:14)”
The stain of sin is, indeed, blotted out by grace, by which the sinner’s heart is turned to God: whereas the debt of punishment is entirely removed by the satisfaction that man offers to God. The priesthood of Christ produces both these effects. Christ was a priest, not as God, but as man, yet one and the same is both priest and God.
The Eucharist obviously ties in with the current topic, as seen in the reply to the second objection: The Sacrifice which is offered every day in the Church is not distinct from that which Christ Himself offered, but is a commemoration thereof. Wherefore Augustine says (De Civ. De. x, 20): “Christ Himself both is the priest who offers it and the victim: the sacred token of which He wished to be the daily Sacrifice of the Church.”
Article 4. Whether the effect of the priesthood of Christ pertained not only to others, but also to Himself?
“In the days of His flesh, with a strong cry and tears He offered up prayers and supplications to Him that was able to save Him from death.” Was the priesthood of Christ effective not only in others, but also in Himself? Thomas told us in question 19 that in His passion Christ offered Himself as a sacrifice, and by His passion He merited, not only for others, but also for Himself.
We read in the acts of the Council of Ephesus “If anyone say that Christ offered sacrifice for Himself, and not rather for us alone, let him be anathema.” Therefore the priesthood of Christ had no effect in Himself.
The sinner needs someone between himself and God, who of himself cannot approach to God; and such a one is subject to the priesthood by sharing in the effect thereof. “For the influence of the first agent in every genus is such that it receives nothing in that genus: thus the sun gives but does not receive light; fire gives but does not receive heat.” Therefore it is not fitting that Christ should receive the effect of His priesthood, for He is the cause of all that His priesthood effects.
Article 5. Whether the priesthood of Christ endures for ever?
It would seem that the priesthood of Christ does not endure for ever, because, at the end of time, the saints in heaven will have no sin, being all just, and there is no redemption for those in hell However, It is written “Thou art a priest forever. (Psalm 109:4):”
The end of the sacrifice which Christ offered consisted not in temporal but in eternal good, which we obtain through His death. The Saints who will be in heaven will not need any further expiation by the priesthood of Christ but will need consummation through Christ Himself, on Whom their glory depends.
Although Christ’s passion and death are not to be repeated, yet the virtue of that Victim endures forever, for, as it is written “by one oblation He hath perfected forever them that are sanctified.”
Article 6. Whether the priesthood of Christ was according to the order of Melchisedech?
“Thou art a priest for ever according to the order of Melchisedech.” In this, the answer seems clear, but we should look at an objection to it by way of reason.
Objection: Christ is the fountain-head of the entire priesthood, as being the principal priest. Now that which is principal is not secondary in regard to others, but others are secondary in its regard. Therefore Christ should not be called a priest according to the order of Melchisedech.
Reply: Melchisedech was not a more excellent priest, but he foreshadowed the excellence of Christ’s over the Levitical priesthood.
As always, there are different ways in which something may be predicated of another. Thomas, the rigorous thinker, is always careful to point out these distinctions, wanting always the clearest understanding possible of the great mysteries of the faith.
Could we say, rather, that Melchisedech was a priest according to the order of Christ? Thomas does not answer this question, but if he did, I would assume careful distinction would be made on the relation of Christ to Melchisedech. Obviously, Melchisedech was not the cause of Christ’s type of priesthood, but Christ was the exemplar cause of Melchisedech’s. What is prior in time is not always prior in cause.
Likewise, Mary is the new Eve, and even though Eve was her “mother” in humanity, Mary is the exemplar of all humanity as human person, the one human person that all of humanity and indeed creation is based on. This is not the place to go into depth here, but I bring it up for its similarity.