How does Faber know he doesn't need to be afraid Montag will turn him in?

Initially, Faber is cautious about discussing novels and helping Montag. After Montag explains his situation, Faber feels comfortable and opens up to him. Faber knows he does not have to worry Montag will turn him in because Montag has already committed several serious crimes against the government. Montag is not only in possession of an extremely rare book (the Bible), but he has also decided to quit his job as a fireman. These are both serious crimes in Bradbury's dystopian society, and Faber realizes Montag is trustworthy because he has already risked his freedom. Faber also recognizes Montag's passion for changing his life. Faber even refers to Montag as a "hopeless romantic" as they discuss why books are important. After Montag pleads for help, Faber gives in and agrees to help him find the meaning of life and challenge the authoritative government.