Huck is not at all fond of religion. In the first chapter of the novel, he tells how Miss Watson and the Widow Douglas are constantly bombarding him with do's and don'ts and attaching religious significance to them. At first when the Widow reads him a story from the Old Testament (Moses), Huck is very interested, but once he discovers that Moses has been dead for a long period of time, he doesn't care anymore because he 'doesn't take stock in dead people'. Then Huck decides he's not really interested in going to the good place (Heaven) because Miss Watson will be there and the bad place (Hell) sounds much more interesting to him. Once he hears that Tom Sawyer will probably be in the bad place, Huck decides that is definitely where he would prefer to be.
Huck doesn't think much of prayer either. In chapter three, Miss Watson tries to teach Huck to pray. Huck believes the purpose of prayer is to get what you want. When he goes for days praying for fishing hooks and they never materialize, he gives up thinking he just can't make prayer 'work'. Later in the novel, Huck tries to pray again as he's deciding whether or not to help Jim to freedom. At first says he will turn Jim in, but quickly realizes he can't pray a lie. He decides instead to help Jim to freedom even if it means he will go to Hell.