This quote by Captain Beatty to Montag takes place when Beatty discovers that Montag is hiding a book in his home. Books in this dystopian society are banned, and it is against the law to have a book in your possession. At this point in the story, Montag is unsure what books mean to him, but Beatty has an idea of what motivates Montag to hide the book. Beatty is making a reference to Jesus’s ability to perform the miracle of walking on water. Beatty recognizes that to Montag books are precious and the key to changing society. Later in the novel when Montag meets Faber, Montag understands that books can actually save the society from ignorance and destruction. It is one reason why he memorizes the books Ecclesiastes and Revelations from the Bible. Like Jesus, Montag and the other hobos who have memorized important knowledge will become saviors and bring back an understanding to what society has lost through the burning of books. They will “spread the gospel” of their knowledge, so to speak, and a new “religion” will rise that “praises” knowledge and free thought.
Beatty is making an allusion to the walking on water miracle by Jesus in hopes of breaking Montag’s spirit that he, too, can one day “save” society with his knowledge. To Beatty, it will take a miracle for the society of Fahrenheit 451 to gain a new faith through knowledge.