Hebrews 7:18-21

18The former regulation is set aside because it was weak and useless

19(for the law made nothing perfect), and a better hope is introduced, by which we draw near to God. 20And it was not without an oath! Others became priests without any oath,

21but he became a priest with an oath when God said to him: “The Lord has sworn and will not change his mind: ‘You are a priest forever.’ ” Psalm 110:4