21 but Jesus became a priest with an oath by the One who said to Him: “The Lord has sworn and will not change His mind: ‘You are a priest forever in the order of Melchizedek.’”
Hebrews 7:21 Cross References - MSB
1 Samuel 15:29
29 Moreover, the Glory of Israel does not lie or change His mind, for He is not a man, that He should change His mind.”
Psalms 110:4
4 The LORD has sworn and will not change His mind: “You are a priest forever in the order of Melchizedek.”
Hebrews 6:16-18
16 Men indeed swear by someone greater than themselves, and their oath serves as a confirmation to end all argument.
17 So when God wanted to make the unchanging nature of His purpose very clear to the heirs of the promise, He guaranteed it with an oath.
18 Thus by two unchangeable things in which it is impossible for God to lie, we who have fled to take hold of the hope set before us may be strongly encouraged.
Hebrews 7:17
17 For it is testified: “You are a priest forever in the order of Melchizedek.”