The author of Hebrews chapter 7 is making a difficult and complex point - Jesus is the new High Priest (V26) of the covenant which does not comply with the rules/law established in the Torah. That is, Jesus was NOT descended from the line of Aaron but from Judah (V13, 14).
So what is he discussing? The material in view is the Levitical covenant. See appendix below.
Therefore, if Jesus, a descendant of the tribe of Judah, is to be a high priest (who should be from the tribe of Levi) then a change of law is required (V12).
Now the "change of law" was only a change in the ceremonial law and not the moral law.
John 10:34 - the reference to "gods" is actually a quote from Ps 82:6 and Jesus reference to "law" is actually an abbreviation for the hendiadys, "Law and the Prophets" signifying the entire OT as in, John 10:34, 12:34, 15:35, 1 Cor 14:21. Compare Matt 5:17, 7:12, 11:13, 22:40, 23:23, Luke 24:44. Sometimes this occurs as "Law and the Prophets and the Psalms, John 1:45, Acts 13:15, 24:14, 28:23, Rom 3:21.
APPENDIX Levitical Covenant – Lev 1-9, 16, 21-27 , Num 3, 4, 8, 18, 25:10-13, Deut 33:8-11. This is an eternal covenant (Num 25:12, 13, Ps 106:30) of salt, Num 18:19.
The Levitical covenant is stated in Num 3:11-13 where God takes the Levites instead of the all the firstborn of each family, thus changing the (informal) priesthood from the firstborn of each family to the (formal) priesthood of tribe of Levi. Several Bible writers refer to this Levitical Covenant including:
- Neh 13:29 – “the covenant of the priesthood and the Levites”
- Jer 33:18, 21 – “covenant with the Levitical priests.”
- Mal 2:4-8 – “the covenant with Levi”
- Num 25:10-13 – the eternal covenant of priesthood was also a covenant of peace and a covenant of “salt” (Num 18:19), ie, very solemn and eternal.
- Isa 54:10 & Eze 34:25 also describes the covenant of peace with the Levites
From other Bible passages we can see what the Levitical covenant was.
- A promise by God to set them apart, ie, make them “holy” (Num 3:12, 13), to be a substitute for the first born in Israel, and to have the primary responsibility for caring for the sanctuary, its ritual services and sacrifices, maintaining and transporting its equipment. Ex 32:25-29. In this way, they became the priests of Israel. All these regulations were contained in Lev 1-9, 16, 21-27.
- Thus, the Levites enjoyed a “blessed” (and privileged) status. Ex 32:29, Mal 2:5.
- The book of Leviticus (and Num 1 & 18) sets out the responsibilities of the Levites in operating the ceremonial rites and sanctuary services and caring for the sanctuary equipment. See also Num 1:53, 18:2, Deut 10:8, 31:9, 25, Josh 3:3, 2 Sam 15:24, 1 Chron 15:26.
- Note that in the Book of Leviticus, the distinction between rules for the Levites/priests and Israelites generally can be USUALLY be determined by to people to whom they were addressed. For example: Lev 1-9 are specifically addressed to the Levites and priests, Lev 11-15 are addressed to the Israelites as a whole and thus applied to all people.
- The purpose of the Levitical covenant was to teach and inculcate the plan of salvation (Deut 33:9, 10, Heb 9:8, 9, 11-14, 10:1-3, Col 2:16, 17). That is, it symbolically taught about salvation by grace through the coming Messiah via His substitutionary death in the place of the sinner. Thus, the sacrifices, Levites, priests and High Priest became a type of Jesus in various ways.
- The token/sign (Heb: “oth”) of the Levitical covenant appears to have been the unleavened bread at the annual festival (Ex 13:6, 9, 16, Lev 24:8).