12 For when there is a change of the priesthood, there must also be a change of the law.
13 He of whom these things are said belonged to a different tribe, and no one from that tribe has ever served at the altar.
14 For it is clear that our Lord descended from Judah, and in regard to that tribe Moses said nothing about priests. (Heb 7:12-14)

Sermon Main Points
1) A priesthood from the tribe of Levi was authorised by the law
2) A priesthood from the tribe of Judah was not authorised by the law
3) A priesthood change requires a law change
4) The priesthood of Christ changes a lot for the Jews
5) The priesthood of Christ changes a lot for non-Christians
6) The priesthood of Christ changes a lot for Christians