Final/secret end wizard mode:
"Journal of the Whills, 7:477."
When George Lucas first created Star Wars, he envisioned an alien race known as the Whills. Here's a quote where he describes the Whills:
"Originally, I was trying to have the story be told by somebody else; there was somebody watching this whole story and recording it, somebody wiser than the mortal players in actual events. I eventually dropped this idea, and the concepts behind the Whills turned into the Force. But the Whills became part of this massive amount of notes, quotes, background information that I used for the scripts; the stories were actually taken from the 'Journal of the Whills.'"
As a matter of fact, Lucas said that the Whills recorded the entire Star Wars saga from what they were told centuries later by R2 in a book known as the Journal of the Whills.
Now while that version of the Journal of the Whills isn't canon, the one that is canon is the one in the leak, which contains numerous poems and teachings about the Force; in a way, it can essentially be regarded as scripture for the Jedi. Some of these canonical scriptures contain phrases like "from a certain point of view", "the Force surrounds us and binds us", and all of what Chirrut recites in Rogue One right before he beats up the stormtroopers in Jedha. So basically people like Obi-Wan and Yoda were quoting scripture from the Journal of the Whills.
In regard to Episode VIII, many have speculated that the book we see in the trailer is the Journal of the Whills because of the fact that it's an ancient tome on what is presumably the first Jedi Temple ever built.