Hebrews 7:21
"(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:)"
Cross References (ranked by relevance)
Psalm 110:4
21
The LORD hath sworn, and will not repent, Thou art a priest for ever after the order of Melchizedek.
Hebrews 7:17
For he testifieth, Thou art a priest for ever after the order of Melchisedec.
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.