Dean and Castiel in “Unfinished Business”

Dean

Cas I need you to promise me something.

Castiel

Of course.

Dean

If I do go darkside you've got to take me out.

Castiel

What do you mean?

Dean

Knife me, smite me, throw me into the friggin’ sun; whatever. And don’t let Sam get in the way, cause he’ll try. I can’t go down that road again man, I can’t be that thing again.