There were comic books like this in the past! I had one each about
Pope John Paul II and
Mother Teresa that my aunt Fran gave to me when I was in middle school.
They were published by Marvel, pre-Disney acquisition, but with the state of the comics industry (lots of the formerly independent publishers have either gone under or been acquired by DC and Marvel, which are subsidiaries of Warner Bros and Disney, respectively) it's hard to point you to a good place.
Have they already got a publisher? Scriptwriter? Artist?
I think your first step is investigating religious publishers or subsidiaries of the same; they may have a graphic novels division accepting pitches and/or submissions.
If you're going self-publishing, I can't help much since I don't know how that works, but I can point you to "how to" series among various comic alliances.
If you're not self-pubbing, I would do a little more research into comic artists' professional associations - they often have a "how to break into comics" type article or three, as well as suggestions for agents/publishers to pitch.