Melchizedek is a character found in Genesis. Abraham gains spoils of war, and then he meets a mysterious priest of the “most high” God. To this priest, Abraham tithes. This priest is named Melchizedek:

Gen 14:17 After his return from the defeat of Chedorlaomer and the kings who were with him, the king of Sodom went out to meet him at the Valley of Shaveh (that is, the King’s Valley).
Gen 14:18 And Melchizedek king of Salem brought out bread and wine. (He was priest of God Most High.)
Gen 14:19 And he blessed him and said, “Blessed be Abram by God Most High, Possessor of heaven and earth;
Gen 14:20 and blessed be God Most High, who has delivered your enemies into your hand!” And Abram gave him a tenth of everything.

Melchizedek is mentioned two other places in the Bible. There is a mention to the “Order of Melchizedek” in Psalms 110 (which is not necessarily a reference to Melchizedek himself). Jesus takes this psalm as a reference to “the Christ” in Matthew 22:24.

The second reference to Melchizedek is a very interesting description in Hebrews 7 (starting in Hebrews 6:19):

Heb 6:19 We have this as a sure and steadfast anchor of the soul, a hope that enters into the inner place behind the curtain,
Heb 6:20 where Jesus has gone as a forerunner on our behalf, having become a high priest forever after the order of Melchizedek.

Jesus is said to have gained the priesthood of Melchizedek. Jesus is said to become a priest “forever” a term also used in Psalms 110 (perhaps the author of Hebrews was identifying Jesus as the subject of the psalm). Melchizedek’s order seems to have been commonly viewed as an eternal priesthood. Those of the line of Melchizedek were in some sense immortal, as the author of Hebrews goes on to claim. This point is less obvious in Psalms 110, although the same ideas could have been around during the writing of this psalm.

Heb 7:1 For this Melchizedek, king of Salem, priest of the Most High God, met Abraham returning from the slaughter of the kings and blessed him,
Heb 7:2 and to him Abraham apportioned a tenth part of everything. He is first, by translation of his name, king of righteousness, and then he is also king of Salem, that is, king of peace.
Heb 7:3 He is without father or mother or genealogy, having neither beginning of days nor end of life, but resembling the Son of God he continues a priest forever.

Melchizedek is said to have no beginning of days. He is said to live forever. He is said to resemble the “Son of God” and be a priest forever. The reference is that Melchizedek is like Jesus (or an argument to the reader that Jesus is like Melchizedek). Recall that Jesus is said to “have become” a priest of the order of Melchizedek in the previous chapter. In any case, Melchizedek looks to be some sort of divine creature within these pages.

Melchizedek is said to be greater than Abraham. This is a very important point to the author of Hebrews, as he is attempting to explain how Jesus is superior to Levite preists:

Heb 7:7 It is beyond dispute that the inferior is blessed by the superior.
Heb 7:8 In the one case tithes are received by mortal men, but in the other case, by one of whom it is testified that he lives.

“Whom it is testified that he lives” suggests the author has access to some sort of reference stating that Melchizedek has not died. From this source, the author appears to have gained the information that Melchizedek has no beginning and no end (verse 3). Very likely this is a reference to texts that existed which are similar to our current texts of Enoch and certain Dead Sea Scrolls legends.

The Dead Sea Scrolls describe Melchizedek as a Messiah figure:

13 But, Melchizedek will carry out the vengeance of Go[d’s] judgments, [and on that day he will fr]e[e them from the hand of] Belial and from the hand of all the sp[irits of his lot.]

The entire text is about Melchizedek but the translator abstracts the text:

The figure Melchizedek in 11Q13 (11QMelch) has usually been described as an angel (Martínze 1992, 176). However, some scholars argue that Melchizedek is a divine title (Van de Water 2006, 75-86). In order to understand the figure of Melchizedek, it is necessary to discuss how the manuscript interprets the Old Testament passages in relation with Melchizedek. 11Q13 interprets a number of verses from Isaiah, Leviticus, and other books in the Old Testament dealing with remission of debts and liberation of slaves at the end of a jubilee cycle as referring to the last judgment.

In Second Enoch (Exaltation of Melchizedek, Slavonic Enoch), Melchizedek is given a virgin birth before the Noahic Flood. Furthermore, he is born fully clothed and ages supernaturally. He is immediately marked for the priesthood:

Sopanim was in the time of her old age and in the day of her death. She conceived in her womb, but Nir the priest had not slept with her.
…
When they had gone out toward the grave, a child came out from the dead Sopanim and sat on the bed at her side. Noah and Nir came in to bury Sopanim and they saw the child sitting beside the dead Sopanim, wiping his clothing. Noah and Nir were very terrified with a great fear, because the child was fully developed physically, he spoke with his lips and blessed The Lord.

Noah and Nir looked at him closely, saying, “This is from The Lord, my brother.” And behold the badge of priesthood was on his chest, and it was glorious in appearance. Noah said to Nir, “Behold, God is renewing the priesthood from blood related to us, just as He pleases..”

Noah and Nir hurried and washed the child, they dressed him in the garments of the priesthood, and they gave him bread to eat and he ate it. And they called him Melchizedek .

Slavonic Enoch is a first century AD text. This is likely a typical view of who Melchizedek was. Taken in conjunction with Hebrews 7 and the Dead Sea Scrolls, Melchizedek is portrayed as some sort of divine agent who functions as a God’s agent in the world. Likely there were other legends that survived about Melchizedek, even informing the Psalms 110 reference to his eternal priesthood. The 4th century Gnostic text, The Coming of the Son of God Melchizedek, identifies Melchizedek as Jesus.

The identification of Jesus as Melchizedek is improbable in the 1st century. In Hebrews, Jesus is being compared to Melchizedek and initiated into the line of Melchizedek. All these events as said to happen after the Levitical priesthood and the law have been formed (events which post-date the first meeting of Melchizedek in Genesis). Hebrews 7:11 reads:

Heb 7:11 Now if perfection had been attainable through the Levitical priesthood (for under it the people received the law), what further need would there have been for another priest to arise after the order of Melchizedek, rather than one named after the order of Aaron?

Jesus had two options for priesthood. Jesus, Hebrews admits, was not descended from Judah, and thus his priesthood had to be through Melchizedek. The author spends some time defending the idea that the Melchizedek priesthood is superior to the Levitical priesthood, thus giving Jesus a preferred status. If Melchizedek was Jesus, this would be the time to state as much to prove Jesus’ obvious superiority. But the argument is that Melchizedek is greater than Abraham who is greater than Levi. Since Jesus is of Melchizedek then Jesus is above Abraham and Levi by Transitive Property.

All these facts put Christians in a strange place when dealing with Melchizedek and Hebrews. The Christian can affirm one of the following:

1. Melchizedek is a divine being (without beginning and end).
2. The author of Hebrews is using the story of Melchizedek in a legendary sense. Like a pastor preaching about Jesus using popular culture (like Star Wars), Hebrews is associating Jesus with Melchizedek.
3. The author of Hebrews believes in a divine being without beginning and end, but is wrong. The book of Hebrews is not canonical, as Luther maintained. Eusebius also mentioned it was a disputed book.
4. That Melchizedek is Jesus (as in the Gnostic text), and texts about Jesus being initiated after the Levite Priesthood and law have been established must be reworked.