The reaction to that touch is very much not something in Sam's control. His cock jerks up into the touch, a little blood starting to fill it. And it would be so simple, just to let Castiel keep touching him, let him get Sam off the way that he wants to.

Sam takes a deep breath, willing down any more reaction before he takes Castiel's hand and brings it up to hold onto. "Cas, no," he says softly, keeping eye contact. "You don't have to get me off for me to know that you're good. I know YOU and I know that's true. You don't owe me anything."