Hebrews 2:2

2.Steadfast, or “firm,” or sure, etc.; that is, it was the word of authority, for God required it to be believed; and that it was authoritative, was made more evident by its sanctions; for no one despised the law with impunity. Then firmness means authority; and what is added respecting punishment ought to be understood as explanatory; for it is evident the doctrine of which God shows himself to be the avenger, is by no means unprofitable or unimportant.