Hebrews 7:21
(For those priests were made without an oath; but this with an oath by him that said unto him, The Lord swore and will not change, you are a priest forever after the order of Melchizedek:)
Psalm 110:4
The LORD has sworn, and will not relent, You are a priest forever after the order of Melchizedek.
Hebrews 7:17
For he testifies, You are a priest forever after the order of Melchizedek.
1 Samuel 15:29
And 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 verily swear by the greater: and an oath for confirmation is to them an end of all strife.