A - Thanks for the question and the compliment! I really do enjoy answering the questions and writing.
Melchizedek is the pagan priest-king that makes an offering to Abraham after he defeats four kings, who had taken Lot captive, in battle. From Genesis 14:
"When Abram heard that his nephew had been captured, he mustered three hundred and eighteen of his retainers, born in his house, and went in pursuit as far as Dan. He and his party deployed against them at night, defeated them, and pursued them as far as Hobah, which is north of Damascus. He recovered all the possessions, besides bringing back his kinsman Lot and his possessions, along with the women and the other captives. When Abram returned from his victory over Chedorlaomer and the kings who were allied with him, the king of Sodom went out to greet him in the Valley of Shaveh (that is, the King's Valley). Melchizedek, king of Salem, brought out bread and wine, and being a priest of God Most High, he blessed Abram with these words: Blessed be Abram by God Most High, the creator of heaven and earth; And blessed be God Most High, who delivered your foes into your hand." Then Abram gave him a tenth of everything."He is considered somewhat mysterious, because he appears here and nowhere else in the Old Testament. But, there are several Jewish traditions about him.
He pre-dates the Jewish priesthood of Aaron and is a foreshadowing of the messianic High-priesthood of Jesus. In the book of Hebrews, which is primarily an exposition of Jesus' priesthood and sacrifice, it talks about Melchizedek - pardon the long quote:
We have this hope as an anchor for the soul, firm and secure. It enters the inner sanctuary behind the curtain, where our forerunner, Jesus, has entered on our behalf. He has become a high priest forever, in the order of Melchizedek.Here we see that the author of Hebrews is saying that Jesus is a priest in the line of Melchizedek for several reasons:
This Melchizedek was king of Salem and priest of God Most High. He met Abraham returning from the defeat of the kings and blessed him, and Abraham gave him a tenth of everything. First, the name Melchizedek means “king of righteousness”; then also, “king of Salem” means “king of peace.” Without father or mother, without genealogy, without beginning of days or end of life, resembling the Son of God, he remains a priest forever.
Just think how great he was: Even the patriarch Abraham gave him a tenth of the plunder! Now the law requires the descendants of Levi who become priests to collect a tenth from the people—that is, from their fellow Israelites—even though they also are descended from Abraham. This man, however, did not trace his descent from Levi, yet he collected a tenth from Abraham and blessed him who had the promises. And without doubt the lesser is blessed by the greater. In the one case, the tenth is collected by people who die; but in the other case, by him who is declared to be living. One might even say that Levi, who collects the tenth, paid the tenth through Abraham, because when Melchizedek met Abraham, Levi was still in the body of his ancestor.
If 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 also. He of whom these things are said belonged to a different tribe, and no one from that tribe has ever served at the altar. For it is clear that our Lord descended from Judah, and in regard to that tribe Moses said nothing about priests. And what we have said is even more clear if another priest like Melchizedek appears, one 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 life. For it is declared:
“You are a priest forever,
in the order of Melchizedek.”
The former regulation is set aside because it was weak and useless (for the law made nothing perfect), and a better hope is introduced, by which we draw near to God.
And it was not without an oath! Others became priests without any oath, but he became a priest with an oath when God said to him:
“The Lord has sworn
and will not change his mind:
‘You are a priest forever.’"
Because of this oath, Jesus has become the guarantor of a better covenant.
Now there have been many of those priests, since death prevented them from continuing in office; but because Jesus lives forever, he has a permanent priesthood. Therefore he is able to save completely[c] those who come to God through him, because he always lives to intercede for them.
Such a high priest truly meets our need—one who is holy, blameless, pure, set apart from sinners, exalted above the heavens. Unlike the other high priests, he does not need to offer sacrifices day after day, first for his own sins, and then for the sins of the people. He sacrificed for their sins once for all when he offered himself. For the law appoints as high priests men in all their weakness; but the oath, which came after the law, appointed the Son, who has been made perfect forever.
--Hebrews 6:19 - 7:28
- Because his sacrifice was not one that had to be repeated continually, like the Jewish priests'
- Because Melchizedek (by Jewish legends) was thought not to have died (others say he is Shem - who hands on the Abram the priesthood). This is because many Jews believed that if Scripture doesn't explicitly state that a person died, then they continued to live.
- Because Melchizedek is both King and Priest, like Jesus. Remember that Melchizedek is king/priest over what later Jerusalem.
- Because Melchizedek offers a sacrifice of bread and wine, which isn't offered again until Christ in the Eucharist.
This is why the liturgical prayers mention Melchizedek and why he is held in esteem by the human authors of Sacred Scripture.
I hope this helps.