'Arise' in the Bible

Then he said to them, "Why are you frightened, and why do doubts arise in your hearts?

Even from among your own group men will arise, teaching perversions of the truth to draw the disciples away after them.

So if perfection had in fact been possible through the Levitical priesthood -- for on that basis the people received the law -- what further need would there have been for another priest to arise, said to be in the order of Melchizedek and not in Aaron's order?