Secure the Blessing. Dean is killed and Sam makes a wish. http://archiveofourown.org/series/34311

'So he closes his eyes, grips Dean's amulet hard enough that it's cutting into his palm, and he makes a wish. I want Mom to be alive. I want Dad to be alive. I want Dean to be alive. I want them to have a home and be safe and I want to remember all of this so I'll be able to protect them if something comes after them. I don't want Mom to die and I don't want Dad to ever have to teach Dean how to be a soldier and...And I don't want to be there with them, because supernatural shit is drawn to me. "That'll do, Sammy," the jinniyah says softly and there's a touch like a whisper against his forehead and the world stops and rearranges itself just for him.'