"I'm good with research."

He likes research, to be fair, so it's not too harsh a punishment. But Castiel knows, and Sam knows, and that makes it punishment enough between them.

For now, he lets his eyes close, exhausted both physically and emotionally. He's brought this on himself, hurting Sam in the process, and he knows he can't get away from that without punishment. He's still glad that it's... mild, for the scope of his failure.