Melchizedek is only mentioned three times in the Bible and seems to be a mystery, until you study the life of Shem, the most honored son of Noah. And the fact that Abraham descended from Shem.
Then Melchizedek king of Salem brought our bread and wine, He was priest of God Most High, and he blessed Abram, saying “Blessed be Abram by God Most High, Creator of heaven and earth. (NIV)
The Lord says to my lord:
“Sit at my right hand until I make your enemies a footstool for your feet.” The Lord will extend your mighty scepter from Zion, saying, “Rule in the midst of your enemies!” Your troops will be willing on your day of battle. Arrayed in holy splendor, your young men will come to you like dew from the morning’s womb. The Lord has sworn and will not change his mind: “You are a priest forever, in the order of Melchizedek.” (NIV)
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? (NIV)
God made a compromise between Shem and Abraham, The Holy city, Abraham called “Jireh” and Shem had called “Salem.” God united both names; and renamed it “Jerusalem”.
Two years after the flood Shem became 100 years old. 260 years later Abram was born and 99 years later was named Abraham. Shem was then 459. For more information about Shem see https://jewishencyclopedia.com/articles/13541-shem.
Noah gave to Shem the priestly garments which he had inherited from Adam.
Shem was born in 2448 BC, and died in 1848 BC, and lived for 600 Years.