'Perfection' in the Bible

Wherefore leaving the doctrine of the first principles of Christ, let us press on unto perfection; not laying again a foundation of repentance from dead works, and of faith toward God,

Now if there was perfection through the Levitical priesthood (for under it hath the people received the law), what further need was there that another priest should arise after the order of Melchizedek, and not be reckoned after the order of Aaron?