Hebrews 7, Jesus Christ, high priest forever after the order of Melchizedek.

Melchizedek was either a real person, king of Salem, later to be named Jerusalem, or he was a Christophany, that is a manifestation of Jesus Christ.

Psalm 110:4b  Thou art a priest for ever after the order of Melchizedek.

Psalm 110:4 The Lord hath sworn, and will not repent, Thou art a priest for ever after the order of Melchizedek.