How could He be the High Priest and the Forgiver of sins at the same time?

St. Cyril the Great often spoke of the hypostatic union between Christ’s divinity and humanity. He says, “He became a High Priest according to His humanity while remaining according to His divinity as the One who accepts the sacrifices offered by all. He is the sacrifice Himself according to the flesh and according to the authority of His divinity, He is the forgiver of sins. In both cases, He is the one Lord Jesus Christ.”⁹⁷³ “It is true that every priest stands during the liturgy and is never counted as one who is seated or of equal in honor to God, but instead the priest worships Him. So Christ is a unique Priest for when He offers the liturgical service — according to His humanity — He is also the one who according to His divinity is seated on the divine throne.”⁹⁷⁴

St. Cyril the Great says that this interpretation is not his own but was previously proclaimed by the Psalmist in Psalm 110, in which he demonstrated the unity of the nature of Christ. That psalm makes it clear that the Messiah is going to be an eternal Priest: “The Lord has sworn, and will not relent, ‘You are a Priest forever, according to the order of Melchizedek’” (Ps. 110:4). The psalm explained at the same time that that Priest is at the right hand of God on the heavenly throne; saying, “The Lord said to My Lord ‘Sit at My right hand, till I make your enemies Your footstool’” (Ps 110:1).

Such connection between Christ’s priesthood, and His sitting at the right hand of God, is in essence Christ’s hypostatic unity in His incarnation, namely, the unity of Christ’s divine and human natures. He is the incarnate God, with His human nature parting not from His divinity not for a single moment nor a twinkling of an eye.

970 Origen, Homilies on Numbers , trans., Thomas P. Scheck (Downers Grove, Illinois: IVP Academic, 2009) 3.3.2: p. 11.

971 St. Cyril of Alexandria, On Hebrews .

972 St. Cyril of Alexandria (PG 68:596–604; 616–625).

973 St. Cyril of Alexandria, On Hebrews .

974 St. Cyril of Alexandria, On Hebrews .

Again, St. Cyril talks about Christ’s priesthood and His hypostatic union saying, “While offering the liturgical ministry according to His humanity, He is at the same time God who is seated on the divine throne.”⁹⁷⁵ Again he says, “About Him it is said that He ‘passed through the heavens’ (Heb 4:14) in the flesh and as God at the same time. For He ascended (in the flesh) to appear before the face of God (for our sake) and at the same time, He ‘passed through heaven’ (as God), to sit as a Son with His Father, above all principalities, even so He came to be like us according to the Divine will.”