Why does Montag tear pages out of the Bible? What effect does this have on Faber?

Montag wants the pages in order to read and memorize the passages. Faber is visibly upset.

His hands, by themselves, like two men working together, began to rip the pages from the book. The hands tore the flyleaf and then the first and then the second page. "Idiot, what're you doing!" Faber sprang up, as if he had been struck. He fell, against Montag. Montag warded him off and let his hands continue. Six more pages fell to the floor. He picked them up and wadded the paper under Faber's gaze.

"Don't, oh, don't ! " said the old man.

"Who can stop me? I'm a fireman. I can bum you!" The old man stood looking at him.

"You wouldn't."

"I could ! "

"The book. Don't tear it any more." Faber sank into a chair, his face very white, his mouth trembling. "Don't make me feel any more tired. What do you want?"