Hebrew 7

Paul teaches the Jews that the Levites were subordinate to Moses or Aaronic priesthood.  Moses was under Abraham, the father of many nation.  And Abraham was subordinate to Melchisedek for -

"...he whose descent is not counted from them received tithes of Abraham, and blessed him that had the promises.
7 And without all contradiction the less is blessed of the better."  (Hebrews 7:6–7)

And Melchisedek was subordinate to Christ for -

"...this man, because he continueth ever, hath an unchangeable priesthood.
25 Wherefore he is able also to save them to the uttermost that come unto God by him, seeing he ever liveth to make intercession for them.
26 For such an high priest became us, who is holy, harmless, undefiled, separate from sinners, and made higher than the heavens..."   (Hebrews 7:24–26)

Thus making clear that the law of Moses does not bring salvation.