Answer
The priest Melchizedek appears in three sections of Scripture. He is briefly introduced in Genesis 14:18–20. In a messianic psalm (Psalm 110:4), David addresses the āorder of Melchizedekā specifically: after describing the victory and glory of the Messiah, David says,
āT³ó±š Lord has sworn
and will not change his mind:
āYou are a priest forever,
in the order of Melchizedekāā (Psalm 110:4).
The author of Hebrews, in speaking of Christ, quotes this verse in Hebrews 7:17. So, Genesis provides background regarding the identity of Melchizedek, Psalm 110 connects Melchizedek to the Messiah, and Hebrews chapters 5, 6, and 7 describe the supremacy of Jesus as the Great High Priest, using Melchizedekās role as an illustration of Jesusā priesthood and kingship.
The Bible utilizes the phrase the order of to point to a lineage. An Aaronic priest would have been a priest according to āthe order ofā Aaron (Hebrews 7:11). These priests would have come from the lineage of Aaron, sharing a similar function and nature. So, another translation of Psalm 110:4 says that the Messiah will be a priest āafter the pattern of Melchizedekā (NET) or āafter the manner of Melchizedekā (ISV).
Genesis 14 describes Melchizedek as the king of Salem (which would later become Jerusalem) and a priest of God Most High. Abram recognized Melchizedekās priesthood through his tithing of the possessions he had taken in battle (Genesis 14:16). Interestingly, this incident took place before the institution of the Aaronic line (part of the Levitical priesthood), which was to mediate between God and man under the Mosaic Law. Melchizedek was not a priest of Israel, as that nation did not exist—Abraham had no children yet. The Levites would not become a priestly tribe for another four centuries.
Psalm 110 describes the messianic nature of Jesusā future rule, with an emphasis on Jesusā eternality. It is in the context of Jesusā kingship (cf. Psalm 110:2) that David writes about the Messiahās being āa priest forever, in the order of Melchizedekā (Psalm 110:4). Priests according to the order of Aaron were not kings but priests alone. However, as the author of Hebrews says, Melchizedek was both a priest and a king (Hebrews 7:1). In the same way, Jesus holds the dual role of king and priest.
The eternal nature of the order of Melchizedek is presented in Hebrews 7:3: āWithout father or mother, without genealogy, without beginning of days or end of life, resembling the Son of God, he remains a priest forever.ā In other words, Melchizedek appears in history with no record of a genealogy or ancestral line, no record of his birth, and no record of his death. The point is, Melchizedek appears to transcend earthly existence; this makes him a type of Christ, who truly does transcend earthly existence as the eternal King-Priest who has no predecessor and no successor in His high office.
One implication of Jesusā priesthood according to the order of Melchizedek is that the Mosaic Law was insufficient to save: āIf perfection could have been attained through the Levitical priesthood—and indeed the law given to the people established that priesthood—why was there still need for another priest to come, one in the order of Melchizedek, not in the order of Aaron? For when the priesthood is changed, the law must be changed alsoā (Hebrews 7:11–12). We needed a better priesthood—an eternal priesthood—to save us from our sins for eternity. We needed Jesus, āone who has become a priest not on the basis of a regulation as to his ancestry but on the basis of the power of an indestructible lifeā (Hebrews 7:16).
A priest is a mediator between God and man. Within the Old Testament, the Aaronic or Levitical priests would make sacrifices on behalf of the nation of Israel (Leviticus 16:1–28). Those sacrifices had to be repeated over and over. Eventually the priest would die, and his work as mediator would cease. Jesus, our High Priest āin the order of Melchizedek,ā is not only our mediator but also our sacrifice (see 1 John 2:1–2). Because of His resurrection, death does not interrupt His work; Jesus remains our eternal High Priest.
Not only is Jesus the sympathetic High Priest (Hebrews 4:14–16), but He is the King as well (Revelation 19:16). Jesus will physically reign as king in Jerusalem (Psalm 110:2), and His kingship will be everlasting (2 Samuel 7:13). Much like Melchizedek was both priest and king, Jesus is also both priest and king. He is the eternal mediator between God and man and the final authority as reigning king, soon to return and establish His physical kingdom in the same city where Melchizedek was from, Jerusalem.