but by doing so you revealed that your beliefs are derived from a book that tells you to have those beliefs.
You do realise that is not an argument at all? That’s like saying “how do you know how to build this ikea bookshelf” “I read the instructions” “But you cannot use the instructions to prove that you are in possession of the ikea bookshelf”
You didn’t ask me why I believed in Christianity. You asked me to specify what parts of Christianity said that salvation is free and then got upset when I referenced letters from the Bible, which is THE collection of documents about Christianity.
I feel like you weren’t actually wanting to reason with this, and were just looking for a way to get me to quote Scripture so you could accuse me of circular reasoning and use your napkin image.