Dean, Dean, Dean. Lucifer said there would be no interruptions and he meant it. The only way Sam was getting in was if he let him in. Granted, it was tempting to let him in while Dean was in the middle of his work to make him entirely aware of what's been going on, it might cause more trouble than he wants to squash tonight.

"Good," Lucifer says, releasing the hold on Dean's hair to lightly run his fingers through it and giving him the freedom of motion he needs. He's willing to give Dean a moment to bring himself to start, but not much more than that.