It’s how Sam’s trust in Dean
“I trust you because you are my brother” (4×01)
turned into faith
“You won’t. When push shoves, you’ll make the right call” (5×18)
then into belief
“I believe in you Dean” (8×14)
to end up into something almost holy
“You will never, ever, hear me say that you, the real you, is anything but good” (10×23)
And bonus:
