'Priesthood' in the Bible

And those of the descendants of Levi who receive the priesthood are authorized by the Law to take tithes from the people, that is, from their brethren, though these have sprung from Abraham.

Now if the crowning blessing was attainable by means of the Levitical priesthood--for as resting on this foundation the people received the Law, to which they are still subject-- what further need was there for a Priest of a different kind to be raised up belonging to the order of Melchizedek instead of being said to belong to the order of Aaron?

For when the priesthood changes, a change of Law also of necessity takes place.

but He, because He continues for ever, has a priesthood which does not pass to any successor.