its from the episode a "very supernautral christmas" sams was suppose to give it to his dad but he never came home for christmas so he gave it to dean as he was there and also was honest about him and told him about demons and stuff.
hope it helps. (:
i know that sam gave it ton Dean as a christmas present. sam had originally wanted to give it to his dad but when his dad didn't show up, he gave it to dean. dean's never taken it off since then
posted over a year ago
Correction Dean dumps it in the trash when cas tells him that God doesnt give a damn about the apcolypse
it was a gift from sam when they were kids... Episode titled "a very suernatural christmas" explains that it was a gift intended for john, but when he didn't show up on christmas morning it was given to dean instead
Sam gave it to him in a very supernatural christmas it was intended for john but he did not show so he gave it to dean but dean dumps it in the trash after cas told him that God doesnt care about the apocolypse