There are a few references to religion, and in particular to the Bible, and they are more positive than negative. When Faber stops to read the Bible, he remarks that it is better than he'd remembered it. He laments the fact that Jesus, like other historical and literary characters, have been changed by the parlour shows, changed into becoming superficial and less profound:
Christ is one of the 'family' now. I often wonder if God recognizes His own son the way we've dressed him up, or is it dressed him down? He's a regular peppermint stick now, all sugar-crystal and saccharine when he isn't making veiled references to certain commercial products that every worshipper absolutely needs.
The implication is that religion and literature used to mean something profound, but in a society where people are pacified by mindless entertainment, none of those belief systems and profound truths in literature have any impact. So, there is a sense (from Faber and perhaps Montag), that the loss of religion and literature (the two being quite similar in the context of the novel) is unfortunate.
In addition to the feeling of loss (of literature and religion), there are moments when Faber uses the language of religion and this could be just a manner of speaking or a direct reference to his belief in God. When Faber and Montag are about to part ways, he tells Montag, "Thanks and God bless you." Faber and Montag come to believe (or "have faith in") the power of literature (and maybe religion or religious literature). They come to believe again that literature can make the world a better place.