Hebrews 7:17-21

For it is declared: “You are a priest forever, in the order of Melchizedek.” The former regulation is set aside because it was weak and useless (for the law made nothing perfect), and a better hope is introduced, by which we draw near to God. And it was not without an oath! Others became priests without any oath, but 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.’ ”