I would start out reassuring my friend that I would remain their friend regardless what they decided. Then I would offer to be a listening ear and let him know if they wanted any resources, I could help with that. Losing one's faith can be a very difficult process since there are all sorts of underlying threats of torture, pain, and rejection. They will receive plenty of pressure to conform; they won't need me to be one more source of pressure. They need the freedom to figure out their own thoughts and feelings.

I would have said, "I can understand that. It happened to me many years ago."

Your initial response was perfect. I hope he will come to you with a more specific answer and some questions. I think it is best to wait for that to happen for several reasons. The primary reason being, he needs ownership of his decision for it to be permanent.

I think it is almost comical that my atheist friends here almost all encourage you to refrain from leading or pushing non belief while almost all religions encourage or demand proselytizing non believers. Atheists are often accused of attempting to recruit while the truth is actually the opposite.

What worked with my son was I gave him a book of Bible stories written for children. I asked him to read the stories and tell me what he believed and what he didn't believe. He did not believe:

1. The Universe was created in 6 days.
2. The Star of Bethlehem could lead people to the place where Jesus was born.

Once he realized that some things in the Bible could not be true, it was easy to point out all the things with Noah's Ark, Jonah and the Whale, Moses parting the Red Sea, etc, that could also not be true.

He seems to be coming around but it is a personal thing and he might take years yet to de-convert. One problem wit believers is that they keep going around in circles. Be supportive but not pushy. In time most people see their god is really imaginary.

Everyone's journey is different.

If your friend wants to ask you anything, he will. When/if he does, answer him.
That's really all you can do.

Just encourage him to continue investigating his doubts and come to his own conclusions.

I think you did well. If your friend asks, then you share your thoughts but I would highlight that it was your position/opinion about things. Even if your friend starts moving away from the faith in religion, he might still have a different position/opinion about things from you.

why do people have a need to convince others what to believe?

I'd probably try to stoke his critical thinking on the topic by asking him some questions starting with why he feels his faith is dwindling and based on that proceed forward.. My goal wouldn't be to deconvert him so much as to get him to critically analyze his faith while he's in the frame of mind to do so before blind faith takes over again..

I just listen to what they're saying, if they ask me for input then I will tell them what I think.

My response would be, "If you would like help sorting out your thoughts and feelings, I would be happy to listen and discuss." And that's where I would leave it until I got a response. He may not be looking for advice.

I would simply say, welcome to reality. I don’t think I would dive into a discussion, but I would say you’re welcome to ask me any questions because I’m sure there’s many you need answered.

I often refer them to resources that are designed to help those questioning their faith. Or if I can ask them questions that I asked myself. The main thing is to let them know it is normal to question ones faith.

I would tell them I've been an atheist all my adult life. I'd let them express their feelings and I'd do it best not to influence them. I don't like people to try to influence me.

I would congratulate him on his quest for a better state of mind (the turmoil of questioning is much better than que quiescence of blind faith). I would congratulate him on his mental growth, and I would be honest with him and with myself by admitting and expressing that his questioning could take him either way; rejection or back to full embrace, and of course, perhaps something in between. I am an antitheist, but I would place friendship above beliefs and I would support him on his journey, wherever it may take him. And if he were to ask me, since he knows my stance about religion, then I would go full force and give him the good news about living free and with full ownership of his mind, and I would do it full force not only because I would want him to know, but also because why would I withhold knowledge from him?; a half measure in my response to him would also be dishonest.

The word "friend" is one that I do not use lightly -- someone I can say anything to and hear anything from without losing my temper or self-confidence.

If you can't be HONEST with a 'friend', perhaps they never were.

I think you are right to let him go there on his own if he wants too. I was once PM'ing on an atheist forums with a very personable and bright English Christian who had a wife and young kid, mostly answering his questions and reassuring him I had no judgment against him on account of his religious stance. As a result he decided he didn't believe any longer. But his enthusiasm was short lived and soon he became miserable and depressed, which made me feel badly. I had no desire for him to drop his belief. As a result I am even more careful now when I talk to believers. I much prefer to move them toward better (ie, less fundamentalist) theology than to get them to switch teams.

I think it is perfectly OK to pose "leading" questions. Like, "In Science a questioning critical mind is encouraged and admired. In religion, it is discouraged in favor of faith and scripture. Why do you think that is?"

I would have told him that personal beliefs are "always evolving!" My personal beliefs have evolved over a lifetime... And are still evolving. I don't want to think like someone else nor would I want anyone else to think like me. There are A LOT of people questioning their beliefs during this pandemic... Look for answers you can reconcile as truthful in general and to/for yourself.

You did the right thing. Don't push him towards any direction. He needs to come to his own conclusion. Just let him know you are there for him if he wants to talk about it.

I think that’s the correct approach. The important factor is that he’s your friend.

I would encourage him to do research on the Bible to see if it is less perfect than what the preachers tell him. Then I would offer my own research to show him that the Bible contains false prophecies and contradictions, and ask him to prove me wrong, if he can.

I would let him advance the process. If you try to unconvert him, he's likely to resist. I know for me it was a process. I did it on my own.

I think you did the kind patient thing. Christians are overwhelmed by preachers. He doesn't need another preacher. He needs to start to think for himself. Depending on his denomination he may have no experience thinking his own thoughts and owning them.

What you did let him know that you are a safe friend with whom he can sort this delicate process out.

He might have some hard days ahead and you want any conversations you have with him to be calm and reasonable dialogues.

What you did was really neat.