Sam's free hand comes up, brushing against Castiel's cheek, thumb just glancing over the corner of Castiel's mouth. His other hand tightens at the back of his lover's head, holding Castiel still as his hips begin to move. Slow, short thrusts that keep Sam buried in Castiel's throat for a few moments before he pulls back, allowing Castiel to breathe before repeating it.

"So good for me, Cas," he murmurs, still watching the other man's eyes. "Such a perfect mouth. Love seeing your lips stretched around me, hear how much you want it." His thumb presses just lightly at the corner of Castiel's mouth, not trying to push in but letting Castiel feel that stretch, too. "Gonna fill you up tonight, angel. Remind your body who you belong to."