It is clear that another High Priest like Melchizedek appeared to us, whose Priesthood was not based on a legal physical descent, but on the power of everlasting life, because Jehovah testified “You [Jesus] are a Priest forever after the order of Melchizedek.”
Therefore the previous Priesthood was cancelled because it was weak and unprofitable, for the law made nothing perfect but a better hope is introduced in Jesus, by whom we draw near to God.
Jesus was made Priest with an oath, (Levitical Priests were made Priests without an oath), because Jehovah swore to Him: “Jehovah swore and will not repent. You are a Priest forever after the order of Melchizedek.”
So Jesus became the guarantee of a better Covenant and the Levitical Priests who were many because they died, were replaced with this Man who has an unchangeable Priesthood because He lives forever.
Therefore He is able to save all that come to know and worship God by Him and He lives forever to make intercession for them, for He is the kind of High Priest that we need: Born of the flesh, but holy, innocent, undefiled, separate from sin and exulted above the heavens.
He doesn’t need to offer up sacrifices every day like the Levitical High Priests, first for their own sins and then for the people’s. He did this once for all when He offered Himself up, because the law make men High Priests who would die, but Jehovah’s oath to His Son consecrated Him forever. Heb. 7: 15-28