OLD TESTAMENT
The Lord has sworn
and will not change his mind,
“You are a priest forever
after the order of Melchizedek.” Psalm 110:4
NEW TESTAMENT
17 For it is witnessed of him,
“You are a priest forever,
after the order of Melchizedek.”
18 For on the one hand, a former commandment is set aside because of its weakness and uselessness 19 (for the law made nothing perfect); but on the other hand, a better hope is introduced, through which we draw near to God.
20 And it was not without an oath. For those who formerly became priests were made such without an oath, 21 but this one was made 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.’”
22 This makes Jesus the guarantor of a better covenant.
23 The former priests were many in number, because they were prevented by death from continuing in office, 24 but he holds his priesthood permanently, because he continues forever. 25 Consequently, he is able to save to the uttermost those who draw near to God through him, since he always lives to make intercession for them.
26 For it was indeed fitting that we should have such a high priest, holy, innocent, unstained, separated from sinners, and exalted above the heavens. 27 He has no need, like those high priests, to offer sacrifices daily, first for his own sins and then for those of the people, since he did this once for all when he offered up himself. 28 For the law appoints men in their weakness as high priests, but the word of the oath, which came later than the law, appoints a Son who has been made perfect forever. Hebrews 7:17-28
Never-changing, Everlasting
I remember the first time I learned that the priests had bells around their robes so that when they entered the Holy of Holies, the other priests would know that they were still alive. I was dumbfounded. I don’t believe there is anything to compare to this in our day.