Hebrews 7:3, 15, 17, 21

without father, without mother, without descent, having neither beginning of days, nor end of life; but made like unto the Son of God; abideth a priest continually.

And it is yet far more evident: for that after the similitude of Melchisedec there ariseth another priest

For he testifieth, Thou art a priest for ever After the order of Melchisedec.

(for those priests were made without an oath; but this with an oath by him that said unto him, The Lord sware and will not repent, Thou art a priest for ever After the order of Melchisedec:)