Complicated History of Matt Murdock's Catholicism
Nowadays, it seems like a no-brainer: "oh yeah, Daredevil, he's religious and yada-yada", but like many things, that wasn't always a case. And is it even a case now?
First of all, what we need to understand, is that it was rather a background feature based on the fact where Matt Murdock lived and worked: Hell's Kitchen, which in the 60s was populated mostly by Irish-Americans who practicle catholicism.
But Hell's Kitchen itself wasn't as significant for earlier Daredevil adventures and practically were taking place across the entire New York and sometimes beyond, whether that be Savage Land or fictional European countries. But besides common expressions and phrases, which every character use regardless of their religion, Matt wasn't explicitly presented as Catholic in any way.
The first direct connection to Catholic faith was made by Jenny Blake Isabella in #119, which revisited Matt's connection to Fogwell's Gym and reintroduced the character Kid Gawaine who became a catholic priest off-screen. The issue doesn't tackle Matt's own beliefs, but that appear to be the starting point.
Matt: What happened to Kid Gawaine, Pop? Since he beat the Phoenix mob, I haven't heard anything about him.
Gawaine: Could be there's a reason for that, Mr. Murdock. But it's probably best summed up by saying the name is now Father Gawaine.
Daredevil Vol. 1 #119
This started sort of shift in Matt's views. The next strong evidence might be found on the pages of... Ghost Rider(?) by Marv Wolfman. There, Matt uses a much more spiritual expression that might indicate his somewhat religious views, which wouldn't be surprise for Ghost Rider, where already mentioned Jenny Blake Isabella introduced super religious narrative, as Ghost Rider battled with Satan and Mephisto appeared to him in disguise of "A Friend", Jesus-like figure. Though, that has no correlation to Daredevil, the presence in Ghost Rider book somewhat influenced the way Matt finds his way with words.
Matt: Heaven help us, for [Death-Stalker] may be the one villain on Earth that can not be stopped.
Ghost Rider Vol. 2 #20
If you think that Frank Miller's run was the first to explicitly state that Matt Murdock is a catholic, well... You both right and wrong. The original run didn't have any indication of such, but Miller's comeback with "Born Again" implies Matt having a more complicated relationship with faith that it was initially presented, since the storyarc brings on a lot of religious imagery and the very name of the arc is referencing a spiritual rebirth, usually used to describe a person who converted to or regained faith. But even then, it doesn't confirm Matt as a regular church-goer or even religious himself.
Though, Frank Miller himself in various interviews refered to Matt as being "Irish Catholic", including a small documentary released as an extra to 2003 movie.
Matt (thoughts): A woman came to me with words of hope. She never told me who she was. She wore a gold cross. I touched it, my fingers never forgot it. It's this cross. This cross.
Daredevil Vol. 1 #230
The first actual instance of comics refering to Matt as Christian is in Ann Nocenti's run.
In #239, Matt reflects on how the variety of forms people exist in must be an evidence of some sort of Designer, and how he's the only person to be able to see this Designer's work in all of its beauty, commenting on him being a lucky guy, as he's not only capable of seeing the world as God intended, but also to have Karen Page by his side. This is an important note, by the way, since Matt's relationship with Karen has a direct correlation with Matt's relationship with God.
Matt (thoughts): People sure come in a lot of strange and wonderful shapes. How can anyone think there isn't a Designer behind all this? But then, I'm the only one who sees this special world. The world of countour and form my radar shows me. Guess I'm just a lucky guy.
Daredevil Vol. 1 #239
Matt starts to go around church much more often and he's seen celebrating Christmas on a regular basis, as well as reflecting on a matters beyond realm of regular humans and much beyond, which leads to Typhoid Mary to refers to him as "merry Christian" in #255. The same conclusion about Matt being Christian is drawn by Mephisto, y'know, a literal Devil, who visits and torments Matt in the aftermath of Inferno event in #266, where he also refers to Matt as "Merry Christian".
Typhoid Mary: Right or wrong, good or evil, what's the difference? Don't you know how close they are? How mated they are? Aren't you ever bad, Merry Christian?
Mephisto: You thought you could punch away MEPHISTO?! A true merry Christian would have turned the other cheek! Hahahahahaha!
Daredevil Vol. 1 #255 / #266
The next issue, #267, is the first occasion of Matt going to confession. He states to Holy Father that his last confession took place "many, many years" ago, and now he repents on his betrayal of Karen, as he was seduced and manipulated by Typhoid Mary, which led to Karen running away from New York once again.
Matt: Father... Forgive me, Father... For I have sinned. It has been... Many, many years since my last confession. I have... Over the years, used my fists to get what I want. I have beaten many men. Just recently, I betrayed the woman I love.
Daredevil Vol. 1 #267
And then, Matt's religion is barely present, beyond his yet another confrontation with Mephisto, as Daredevil travels to Hell dimension. In the end of Nocenti's run, in Matt's belongings Foggy also found a cross, and even says that Matt was so distant in general, that Nelson had no idea he was even religious, and they were friends for like eternity.
Foggy: And this gold cross-- Funny, I didn't expect you to have a cross. But it makes sense now.
Objects, what good are they? All I remember is your face... That look on your face when you stood in the courtroom as I defended a chemical company that blinded a little boy... From the idealism of law school-- to the ugly practice of law.
Daredevil Vol. 1 #291
Then Matt's faith was thrown away in the box, up until "Guardian-Devil", which appears to be the primary source of religious traits Matt has in TV show, since both Vol. 2 and Netflix show were produced by Joe Quesada, as an editor of Marvel Knights and producer in Marvel Television.
In Karen Page's letter, she refers to Matt's faith being strong, she also mentions that he visits Sunday Mass and jokes about Karen herself not being "a woman of faith". The scene of Matt visiting the confession again, as he again reflects on Karen leaving him, served as main source of inspiration for 1x01 opening, according to Charlie Cox.
Matt: Forgive me, Father-- For I have sinned. It's been... Far too long since my last confession. Six months ago, my girlfriend left me...
Daredevil Vol. 2 #1
"Guardian-Devil", alike to "Born Again", plays a lot with religious imagery and subtext, but does so much explicitly, including an already established motiff of Devil/Angel dichotomy Matt/Karen's relationship had, which was the only somewhat spiritual notion during 90s runs, where Karen adopted the secret identity of radio host Paige Angel.
Matt not only visits church yet again, he asks Doctor Strange to help interrogate Mephisto one more time, who mocks Matt for his lack of knowledge about Apocalypse prophecy of Second Coming, which would indicate that no matter how much more religious Matt is presented in the arc, he's actually not as well-informed about Bible, which alignes with Nocenti's presentation of Matt as Lapsed Catholic, person who believes but does not practice.
Mephisto: Why is one so mighty as myself brought here to instruct as a Sunday School Teacher?
Have your Christian friend read his Bible? More specifically, the apostle John's Book of Revelations? <...> Now, I'm no literary major, but I'd say the text is indicating a far different manifestation of the so-called redeemer than as a human infant.
Matt (thoughts): My God... He's right. Biblically, the savior is to come back as he left-- A man.
Daredevil Vol. 2 #5
The same issue is the last time Matt would visit church before he returns there in Soule's run many-many years later, since in Daredevil Vol. 2 #5 an event happens that would drift Matt away from his religion far more than before, and that is Karen's death.
Since that moment, Daredevil books would yet again ignored any sort of religion of the title character, and focused more on the impact Karen's death left on Matt, as he gradually fell into the darkness, eventually leading to him becoming Kingpin of Hell's Kitchen, and then taking over the Hand, possessed by The Beast, another demonic entity.
Somewhere in between, though, Matt is reminded of the existence of afterlife by Copperhead in "Spider-Man/Daredevil" limited series, as Matt attempts to kill himself. The villain teases Daredevil with the notion that he'll never reunite with Karen in death, as "good little Catholics" end up in Hell if they commit suicide, and it stops Matt from pulling the trigger.
Copperhead: Does a suicide that saves other count as a suicide? What if you God abandons you?
That's what happens to good little Catholics who take their own lives. There's no forgiveness for the mortal sin you're about to commit. That coked-up little jezebel you loved so well -- If you pull the trigger, will you ever see her again in the eternity?
Matt: ...Karen...
Daredevil/Spider-Man Vol. 1 #4
As was mentioned, the next time Matt actually visits church is Vol. 5 #15. He's going through another personal crisis after his apprentioce, Sam Chung, was blinded by the Muse. Matt goes in disguise and refuses to confess, prefering just have a talk with a priest. He directly states that Karen's death was the reason he actually stopped being a Catholic, and thus believing in God.
Matt: I'd been a believer up until that point. But when that happened... I decided that either God didn't exist, or His sense of morality was so alien that I would never be able to understand it. Ever since then... I've made my own way.
Daredevil Vol. 5 #15
Father Jordan, a priest who runs a church, reveals himself as a member of an ancient cabal known as Ordo Draconum, a Catholic Knight order formed to battle with various sorts of evil, mostly vampires. He convinces Matt to regain his faith, and in the next issues, Matt return to confession in order to reflect on him erasing world's memory about him being Daredevil with the help of Purple Children.
When Matt tries to reconnect with Foggy, he says he returned to being Catholic as a proof of him changing for the better, reminding us that he hasn't been a believer ever since Karen's death.
Matt: I'm saving lives, Foggy. And things have changed for me. I've started going to church again, for the first time since... Since Karen.
I'm trying to do it better this time. Trying to do it right.
Daredevil Vol. 5 #24
The later part of Soule's run seems to implement more of Matt's faith, revitalized by Netflix series, in which he became a devout Catholic, rather than lapsed one, in addition to artstyle trying to replicate actor's likeness. A classic example of so-called MCU synergy that's been happening with comics in late 10s.
So, by the time when Season 3 concluded, the mass audience has been hooked onto belief that Matt is very-very religious character, which was exagerrated even more in following run by Chip Zdarsky, who retconned Matt's biography by flashbacks, where he visits church in his first black outfit presented in semi-canonical "Man Without Fear" by Frank Miller.
It kinda ignores Matt's faith evolution and just makes it a ground zero trait of his, as if he wasn't struggling with his beliefs on a much more severe level. It doesn't give a single mention of why he became so devout, besides the implication that this is a result of Matt having a near-death experience in the finale of Soule's run (where he almost did reunite with Karen in death) and his hard recovery in "Man Without Fear" by Jed MacKay.
You know the rest, as Zdarsky practically just borrows elements from Netflix series onto 616 and steps even further. In Ahmed's run, Matt temporarily became a priest himself, battled with Seven Deadly Sins, and now, in Stephanie Phillips' run he's kinda again isn't very much of a religious guy. At least, as of first 4 issues that released. Maybe the situation will change in upcoming storyarcs?