The Westminster Shorter Catechism
Q25. How doth Christ execute the office of a priest?
A. Christ executeth the office
of a priest, in his once offering up of
himself
a sacrifice
to satisfy Divine justice,[1] and reconcile us to God;[2]
and
in making continual intercession for
us.[3]
[1] Hebrews 9:14, 28; [2] Hebrews 2:17; [3] Hebrews 7:24–25; 12:24–25.
While a prophet is God’s representative to men, a priest is a man who represents men to God by offering up sacrifices and making prayers on their behalf (Heb 5:1; 8:3). This is what Christ, as our priest, does for us. The author of Hebrews tells us that this was one of the chief reasons why Jesus took on the nature of man rather than of angels, for only as man can He be a merciful high priest (Heb 2:16–17). But how could Jesus be a priest when He is descended from Judah rather than Levi? The answer lies in the fact that He was anointed a priest in the order of Melchizedek with an oath (Heb 5:6; 7:15–17; cf. Ps 110:4). By design, the Melchizedek priesthood is already a higher priesthood than the Aaronic priesthood since Abraham, who is the ancestor of Levi, gave tithes to Melchizedek (see Heb 7:1–10). But more than that, Jesus’ priestly ministry is far superior to the ministry of the Aaronic priests.
Firstly, He needs not offer any sacrifice for Himself since He is without sin,
though He was in all points tempted like as we are (Heb 4:15; 7:27).
Secondly, rather than offering animal sacrifices which are but shadows and types
which cannot take away sins (Heb 10:4), Jesus offered Himself, the antitype
which all the OT sacrifices were pointing to (Heb 9:14, 28). In doing so, He
not only propitiated the wrath of God by vicariously taking the punishment for
sin that is due us upon Himself, but reconciles us to God (Heb 2:17; Eph 2:16).
Notice how the Catechism highlights that His offering is once for all rather
than repeated (cf. Heb 9:26, 28; 10:10). This not only refutes the Roman
doctrine of a sacrificial mass, but also demonstrates the sufficiency of His
atonement, He being both God and Man.
Thirdly, unlike the Aaronic priests, Jesus continues ever to make intercession
for us (Heb 7:24–25; 12:24–25). Moreover, He does not intercede for us on earth
as the Aaronic priests would have; rather, He is exalted to the right hand of
God the Father, and He intercedes for us there (Rom 8:34). What does He
intercede for? As our advocate, He pleads with God that on account of the merit
of His death our sins may be pardoned; our consciences quieted and our souls
preserved: “If any man sin, we have an advocate with the Father, Jesus Christ
the righteous” (1 Jn 2:1). As our mediator, Christ beautifies our prayers by
removing all impurities and sin, and then, presenting them to the Father,
pleads that such as made in His name and in the will of God may be answered:
“If ye shall ask any thing in my name, I will do it” (Jn 14:14).