In chapter 1, many examples surface about religion.
First, when Miss Watson begins explaining about Moses, she intends to teach Huck principles and values of religion, but what he takes from it is what could be a good current story about adventure and someone he'd like to meet. Here we see his disappointment in religion:
"...she let it out that Moses had been dead a considerable long time; so then I didn't care no more about him, because I don't take no stock in dead people."
When the opportunity came to further teach Huckleberry about the purpose of obedience, she cites the advantages of heaven but Huck did not really find the good in it, so he determines he'd prefer hell:
"She said it was wicked to say what I said; said she wouldn't say it for the whole world; she was going to live so as to go to the good place. Well, I couldn't see no advantage in going where she was going, so I made up my mind I wouldn't try for it. But I never said so, because it would only make trouble, and wouldn't do no good.
Now she had got a start, and she went on and told me all about the good place. She said all a body would have to do there was to go around all day long with a harp and sing, forever and ever. So I didn't think much of it. But I never said so. I asked her if she reckoned Tom Sawyer would go there, and she said not by a considerable sight. I was glad about that, because I wanted him and me to be together."
This proofs of Huck failing to understand religion both occur in the first few pages. This is significant because the book will take a turn in regards to theme, but I think it is a critical comment to spite religion on pages 1-2. Twain wants to prove that the notion of Christianity as it was did not do what it claimed to do. Otherwise, slavery would never have been an issue.
Later in the book, Huck makes up his mind about not selling Jim or turning him in. He understands the legal wrong that such a decision would cost him. It may indeed land him in jail, but he confuses it with hell. His decision will land him in God's grace, but he has been so trained that he is bad that he confuses the moral, godly and legal rights of the world.