“Without father, without mother, without genealogy, he has neither beginning of days nor end of life but is like the son of God, and he remains a priest for all time” (Hebrews 7:3).
The Old Testament book of Ezra chronicles the return of a group of Israelites who had been deported from their ancestral homes by the ancient Babylonians (see Ezra 1:1-3). However, one group of Israelites who made that return trip were prohibited from resuming their former duties…
“Three families of priests… also returned. …They searched for their names in the genealogical records, but they were not found, so they were disqualified from serving as priests” (Ezra 2:61-62 NLT).
This brief excerpt illustrates the importance of an ancestral registry in respect to the Old Testament priesthood. That priesthood was established in the Biblical book of Exodus based on God’s directive to Moses…
“Now take Aaron your brother, and his sons with him, from among the children of Israel, that he may minister to Me as priest, Aaron and Aaron’s sons: Nadab, Abihu, Eleazar, and Ithamar” (Exodus 28:1).
This is an important point in the context of Hebrews chapter seven. The Old Testament priesthood was limited exclusively to the descendants of Levi through the family of Aaron. Everyone else was excluded. On one occasion when someone who was not genetically linked to Aaron attempted to fulfill a priestly role, the results were disastrous (see 2 Chronicles 26:16-20).
Because of this, it is important to note that Melchizedek’s priesthood was based on a different order from the one held by those who were descendants of Aaron. Unlike the members of the Levitical priestly class, Melchizedek’s priesthood did not depend upon a specific genetic lineage. One source explains the nature of that priestly ministry…
“…it is the reverse of the rules which governed the Aaronic priesthood which depended entirely on descent. Under Jewish law a man could not under any circumstances become a priest unless he could produce a certificated pedigree going back to Aaron. Character and ability had nothing to do with it; the one essential was that pedigree.
…On the other hand, if a man could produce a pedigree reaching back to Aaron, apart only from certain specified physical blemishes nothing on earth could stop him being a priest. Genealogy was literally everything. So then, the first difference between the two priesthoods was this–the Aaronic priesthood depended on genealogical descent; the priesthood of Melchizedek depended on personal qualification alone. Melchizedek’s priesthood was based on what he was, not on what he had inherited.” (1)
(1) Barclay, William. William Barclay’s Daily Study Bible, “A Priest After The Order Of Melchizedek (Heb 7:1-28)”