Context, context!
The writer of the book called "to a group of Messianic Jews" or Hebrews is quoting Psalm 110:4
4 The LORD has sworn and will not change His mind, "Thou art a priest forever According to the order of Melchizedek."
b'shem Y'shua
NASBu Psalm 110:1 A Psalm of David. The LORD says to my Lord: "Sit at My right hand, Until I make Thine enemies a footstool for Thy feet."
2 The LORD will stretch forth Thy strong scepter from Zion, saying, "Rule in the midst of Thine enemies."
3 Thy people will volunteer freely in the day of Thy power; In holy array, from the womb of the dawn, Thy youth are to Thee as the dew.
4 The LORD has sworn and will not change His mind, "Thou art a priest forever According to the order of Melchizedek."
5 The Lord is at Thy right hand; He will shatter kings in the day of His wrath.
6 He will judge among the nations, He will fill them with corpses, He will shatter the chief men over a broad country.
7 He will drink from the brook by the wayside; Therefore He will lift up His head.
Yes, I know that quote is from the Psalms.
It changes nothing of what I said, but it's a nice try at a diversion. Do you have anything substantive to say?