Castiel's trembling lips open and close in what can only be interpreted as a plea, voicelessly begging for release, his own and Sam's, because he's on the verge of breaking on that peak, needs to feel Sam come warm and hot and deep inside of him, to seep deep into Castiel's core and stay there as part of him, in more ways than one. And the only word he can manage, voice wreck and almost faint, eyes feverish with love and adoration... is "Sam."