Psalm 110:4

4 The LORD has sworn and will not change his mind: “You are a priest forever, in the order of Melchizedek.”

Read Psalm 110:4 Using Other Translations

The LORD hath sworn, and will not repent, Thou art a priest for ever after the order of Melchizedek.
The LORD has sworn and will not change his mind, "You are a priest forever after the order of Melchizedek."
The LORD has taken an oath and will not break his vow: “You are a priest forever in the order of Melchizedek.”