Hebrews 7:21
(for they indeed have been made priests without an oath), but he with an oath by him that says of him, "The Lord swore and will not change his mind, 'You are a priest forever, according to the order of Melchizedek.'"
Psalm 110:4
Yahweh has sworn, and will not change his mind: "You are a priest forever in the order of Melchizedek."
Hebrews 7:17
for it is testified, "You are a priest forever, according to the order of Melchizedek."
1 Samuel 15:29
Also the Strength of Israel will not lie nor repent; for he is not a man, that he should repent."
Hebrews 6:16-18
For men indeed swear by a greater one, and in every dispute of theirs the oath is final for confirmation.