Even if it was not religiously connected, Charlie may have some reason to make amends. He dealt with his brother's drug abuse, so I'm sure Charlie is aware of any number of 12 step programs. One of the steps is to apologize to those you have wronged and seek their forgiveness.

Charlie was still trying to overcome his addiction when he kidnapped Sun. I don't think many know of his addiction problems, unless Claire and a couple of others have made it common knowledge.

It's still a spiritual act regardless of whether it is religious in nature.

Just a thought.