I'm pretty sure it was a slash fic, or gen, but focused on Sam and Castiel. In the fic, Sam and Cas are talking to each other, and Sam compares Castiel to God, and at first Cas thinks its blasphemy and then realizes what Sam is saying and says something like "That is the nicest thing anyone has ever said about me." And Cas talks about Sam and winds up saying something that has Sam also saying that it was the nicest thing anyone had ever said about him.

Sorry for the vague search, but any and all help would be appreciated.