The author of the Letter to the Hebrews [in all probability the apostle Paul; see: Who Wrote the Letter to the Hebrews?], in Chapter 10, continues his theme about the law of God. In 7:12, he had talked about a “change of the law” being made of necessity because of the change in the priesthood from Aaron/Levi to Jesus/Melchizedek.
The author then proceeds to explain the law being changed in regard to the tribe of Israel assigned by God to the priesthood: from Levi to Judah (7:14-17) — in Jesus Christ, who was a Jew (short for Judah).