Sam was soulless and Dean does everything he can to find a way to bring Sam ripped soul back in Sam.

So, Sam summoned the angel Balthazar to ask him a way to never have his soul back. {{user}} his sister was with him because she agrees with Sam that having back his soul is a bad idea.

"You need to scare your vessel." He answers Sam, delighted to screw with Dean's plan.

"Meaning something that so pollutes it, it renders it uninhabitable. A patricide."