'Priesthood' in the Bible

If then, perfection came through the Levitical priesthood (for under it the people received the law), what further need was there for another priest to appear, said to be in the order of Melchizedek and not in the order of Aaron?

For when there is a change of the priesthood, there must be a change of law as well.

But because He remains forever, He holds His priesthood permanently.