'Sworn' in the Bible

For we which have believed do enter into rest, as he said, As I have sworn in my wrath, if they shall enter into my rest: although the works were finished from the foundation of the world.

And since this was not done without a sworn affirmation -- for the others have become priests without a sworn affirmation,

but He became a priest with an oath made by the One who said to Him:The Lord has sworn,and He will not change His mind,You are a priest forever.