The priesthood under the Law has always come from the tribe of levi(Aaron) BUT under Gods Promise, the Priest must come in the order of Melchizedek. As it says: The Lord has sworn and will Not change His mind: You are Priest forever. Ps 110:4(Heb7;21)
You are a Priest forever in the order of Melchizedek.
It is because the Law made Nothing Perfect, Heb 7:19
so, the law has to change Heb 7;12
There are two laws, the priesthood laws under the Levites was what was written in the book of the law, not the Ten Commandments.
Deut 31:24 So it was, when Moses had completed writing the words of this law in a book, when they were finished, 25
that Moses commanded the Levites, who bore the ark of the covenant of the Lord, saying: 26 “Take this Book of the Law, and put it beside the ark of the covenant of the Lord your God, that it may be there as a witness against you;
This is what was written and put beside the ark. Not what was inside the ark God’s eternal Ten Commandments.
Hebrews 7 is addressing the law of priesthood because the law said all priests needed to come from Levi because the Levites were the only ones who were faithful while Moses went up to get the Ten Commandments. Jesus coming from the tribe of Judah caused an issue under the law so the necessity of the aw had to be changed, which is what Hebrews 7 is all about.
There is a law that not a jot or tittle can be changed and a law that was temporary. We already see in the law of Moses the priesthood changed, animal sacrifices changed which means that is not the unchangeable law Jesus was referring to. It is obviously the Ten Commandments written by the finger of God, the laws Jesus quoted from when He said not a jot or tittle can be changed Mat 5:18 because He promised He would not alter His Words Psa 89:34. At some point we need to start believing God and what He taught, everything else really is only a snare that I fear will not end well according to the Words of Jesus Christ Mat 7:21-23 Rev 22:14-15
We don’t have to agree, thats okay, but our time here is short and once Jesus comes back all decisions are final Rev 22:11