A king-priest with no genealogy meets Abraham with bread and wine. Hebrews builds a whole chapter on him: change the priest, and the entire law changes with it.
The Shadow
Abraham is returning from battle when a man appears who has never been mentioned before: Melchizedek, king of Salem, priest of God Most High, carrying bread and wine. He blesses Abraham, receives a tenth of everything, and vanishes from the narrative. His name means king of righteousness; Salem means peace. Righteousness first, then peace, the exact order of the new covenant. A thousand years later David wrote one line about him that became the most quoted psalm in the New Testament: “You are a priest forever according to the order of Melchizedek.”
The Fulfillment
Hebrews 7 builds the argument. Melchizedek has no recorded genealogy, no beginning of days or end of life, made like the Son of God, a priest continually. Under Levi, your family tree was your credential and every priest eventually died, so the intercession expired every generation. And since Levi was still in Abraham's body when Abraham gave the tenth, the old priesthood bowed to this one before it was born.
Then the hinge verse: the priesthood being changed, of necessity there is also a change of the law. Change the priest and the whole system changes. Jesus came from Judah, a tribe with no priestly credentials, on purpose, so no one could mistake the new covenant for a renovation of the old. And because He continues forever, He is able to save to the uttermost, since He always lives to make intercession.
Him All Along
If you measure your access to God by the quality of your week, bold on Sunday and bankrupt by Thursday, you are living under Levi: a covering that wears off and a ledger that resets. There is no ledger. The account was settled once, by blood that does not need reapplying, held by a priest who will never be replaced. He is a priest forever, and forever has no expiration date.