[ Sam is a good person with a good soul, and somehow Castiel thought that, even deprived of it, Sam would still act the way he had, like riding a bicycle, so to speak.
Instead he gets this: a problem that, rather than comforting Dean, endangers him. Cas sees now that, until Sam's soul can be retrieved, he's a liability. As he holds Sam by the neck and looks into his eyes, he sees the cold, gooey emptiness there, and it scares him. There is reasoning with demons and monsters. There is no reasoning with this. His right hand remains on Sam's neck, but his left drops to Sam's chest. ]
"And the lord said unto him, therefore whomsoever slayeth Cain, vengeance shall be taken on him sevenfold."
[ "And the Lord set a mark upon Cain, lest any finding him should kill him." With an ear-piercing whistle, Castiel's hand, pressed to Sam's chest, begins to glow, and Sam will feel a burning like the muscle of his chest is being peeled away in quick pieces, but there's no marks there on his shirt or on his skin, only pain.
The pain is over quickly, horrible and tortuous for only a few seconds, and then only the sting of it remains. Between one blink and the next, Castiel takes Sam's advice and is gone. ]
cw: description of gore
Instead he gets this: a problem that, rather than comforting Dean, endangers him. Cas sees now that, until Sam's soul can be retrieved, he's a liability. As he holds Sam by the neck and looks into his eyes, he sees the cold, gooey emptiness there, and it scares him. There is reasoning with demons and monsters. There is no reasoning with this. His right hand remains on Sam's neck, but his left drops to Sam's chest. ]
"And the lord said unto him, therefore whomsoever slayeth Cain, vengeance shall be taken on him sevenfold."
[ "And the Lord set a mark upon Cain, lest any finding him should kill him." With an ear-piercing whistle, Castiel's hand, pressed to Sam's chest, begins to glow, and Sam will feel a burning like the muscle of his chest is being peeled away in quick pieces, but there's no marks there on his shirt or on his skin, only pain.
The pain is over quickly, horrible and tortuous for only a few seconds, and then only the sting of it remains. Between one blink and the next, Castiel takes Sam's advice and is gone. ]