"Whoever said Dean was the dysfunctional one has never seen you with a sharp object in your hand."
It made Gabriel sad. He knew Sam's destiny. He was going to be the bad guy in this story. If he could get him to understand that he couldn't save Dean, he might be able to short-circuit this whole plan. If Sam weren't hell bent on saving Dean (pun intended), then he won't be susceptible to Ruby's manipulations.
"Bring him back, please," Sam begged.
Right then and there, Gabriel knew it was over. He would give Dean back to Sam for a couple of more months. It was all he could do.