Often times in movies or television shows, Heaven is depicted as an office with angels bustling around, checking the weight of good versus bad souls and filing prayers by order of importance, urgency or even worth. Like that movie Bruce Almighty where Morgan Freeman has the little bitty filing cabinet full of the entire worlds prayers and Ace Ventura pulls open the drawer and goes flying across the room.
Heaven isn't anything like that.
Not that anyone would assume it was, but its kind of Gabriel's hometown so it's a bit of a sore spot.
The only thing they remotely get right are the prayers. They do come flooding into Heaven all willy-nilly and have to be organized according to the Host's filing system (spoiler alert: it's alphabetical, nothing special). The majority of them don't get answered and some of them don't even get read (it may be Heaven, but it's not perfect, okay?) but those are the ones that tend to work themselves out anyway or are the ones that are the stuff of middle school dances ("Dear God, please let Amanda say yes to dancing with me!").
But the thing is, Gabriel has always loved them. When the human race was newly formed and prayers first started flowing in, he'd sit for hours reading until Michael literally dragged him away by his wings (and people wonder why Gabriel is resentful?). Lucifer never understood his brother's fascination, couldn't be bothered to read what the humans were 'whining' about.
When he left Heaven, he left with knowledge of the Winchesters and the role they would eventually play in the end-all contest between two brothers who couldn't be bothered to love each other anymore.
Gabriel decided he'd 'earmark' the brothers (so to speak). Being an archangel comes with all sorts of perks, so he got any and all prayers from the Winchesters sent directly to him first before they got spun off into the clusterfuck of Heaven. Dean's start to filter in and they're normal for a kid whose mom is obviously prodding and watching over as he kneels by his bedside. Eventually, the prayers shift from 'Keep Daddy and Mommy safe' to 'Keep Daddy and Mommy and the new baby safe'. It becomes 'Keep Daddy and Mommy and Sammy safe' and then six months later they stop altogether. Gabriel knows why. He knows what happened to Mary Winchester and he feels…regret. Regret that Dean got so little time with her and Sam got even less. Regret that John chooses revenge over raising his boys the way Mary wanted, away from everything that was forced on her growing up.
After lifetime upon lifetime of punishing mortals for their transgressions—and the performing some of the duties of a demi-god (no horses ever again, please)—feeling regret leaves Gabriel feeling uncomfortable and it niggles at the back of his mind like an itch he can't scratch.
When Sam's old enough, he starts to pray filling up the radio silence Dean's been broadcasting for years. The younger Winchester's prayers are simple early on, much like Dean's were. 'Keep Daddy and Dean safe and take care of Mommy in Heaven' is the most common and regret rears its ugly head again. Every so often, the prayers of an awkward little boy tired of moving across the country filter in; 'Please let the kids in school like me' or 'Help me find something nice for Dean for Christmas' or 'Let us stay, just for a little while. I like it here.'
There's another shift when Sam finds out about what it is John and Dean are actually doing. It's probably around the same time he gets his first gun, Gabriel reasons. 'Please let Dad and Dean kill the monster' and 'please make it so I never have to use this stupid gun'.
Sam gets out and goes to California for college but he never once stops praying for his dad and brother. They're interspersed with requests for good grades and for a girl named Jessica to notice him, but they're there despite the manner the Winchester's had parted ways. When Dean comes to him and asks for his help, Sam goes. He acts like he'd rather pull out his own teeth, but Gabriel has been listening to Sam's prayers for the boy's entire life and he can practically feel his elation at seeing Dean again after so long.
Sam prays through the hunt, for Dean and his Dad and Jessica back at Stanford. He prays for his mother in Heaven. And when he returns and finds the woman he loves has been murdered Sam prays that he'll find the yellow-eyed bastard who started this and finally put an end to him.
He doesn't stop praying when he hunts with Dean, the same base of 'Keep Dean and Dad safe. Let Mom and Jessica be happy.' Occasionally he prays for help and Gabriel can't resist. He drops a book Sam needs in the freshly returned pile at the library or highlighting an important passage in an online article. Every once in a while he hears the Winchesters pray to his little brother Castiel. It's mostly Dean, but sometimes Sam. Gabriel smiles and wonders what his brother has gotten into.
Sam keeps praying and Gabriel collects them all greedily, hordes them to himself, files them away.
He meets the Winchesters three times but he never stops amassing and cataloguing and arranging Sam's prayers. They flow through his grace and he sometimes goes back to the ones before the hunting and the grief and just recites the words of a little boy who loved his family. Gabriel realizes that Sam has never really changed from that little boy. Family still comes first, always. For the first time, an archangel feels jealousy.
And then one day the prayers stop.
Gabriel is lost.
He discovers that Anna, working under orders from Heaven, has tried to kill Mary and John Winchester in order to prevent Sam's birth. He's never felt such rage. Sam has given up on Heaven. Given up on the insane hope that someone is listening. Gabriel wants to scream that he is. He's listening and has been for years. But he can't tell Sam that. Can't tell him that his words—the words of an awkward little boy—are what make the archangel choose the side of free will and family even as he acts directly against his own.
He faces off against his brother in the hotel, sword drawn and ready. Gabriel knows there's a slim chance of this plan working but he does it any way. He raises his sword behind Lucifer and he hears it.
'Let Gabriel make it out alive. Please.'
He doesn't have time to smile before a searing pain and blinding light engulf him.