​How can I write a religious character arc

(Repost since the original post was very vague)
Ive been working on this dark fantasy story for a while but recently I’ve been struggling on how i should go about writing a religious character arc for one of my main characters where the characters gains faith that he previously didn’t have.

I want the character arc and conversion to feel realistic and to actually mean something beyond the character just being religious for the sake of being religious , and I don’t want it to feel like I’m “forcing religions beliefs” on the reader.

The two reasons I want to add a religious character arc
1.The main inspiration for the character is actually a saint called Saint Moises the Ethiopian who was a bandit and band leader before he was a monk

2.I feel like it fits his character well since I wrote the story as just a long redemption story where he goes from being a nihilistic , earnest and rude person to a person who lives a life of regret for all he has done