Psalm 110:4 in the King James Version
The LORD hath sworn, and will not repent, Thou art a priest for ever after the order of Melchizedek.
Context
3 Your people offer themselves willingly in the day of your power, in holy array. Out of the womb of the morning, you have the dew of your youth.
4 The LORD has sworn, and will not change his mind: “You are a priest forever in the order of Melchizedek.”
5 The Lord is at your right hand. He will crush kings in the day of his wrath.