Hebrews 7:21-24

(for they indeed have been made priests without an oath; but he with an oath by him that saith of him, The Lord sware and will not repent himself, Thou art a priest for ever); by so much also hath Jesus become the surety of a better covenant. And they indeed have been made priests many in number, because that by death they are hindered from continuing: but he, because he abideth for ever, hath his priesthood unchangeable.