Hebrews 7:21-24

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

22Because of this oath, Jesus has become the guarantor of a better covenant. 23Now there have been many of those priests, since death prevented them from continuing in office; 24but because Jesus lives forever, he has a permanent priesthood.