The Book

He believed that God, whom he affectionately called the S.F. or Supreme Fascist, had a transfinite book (“transfinite” being a mathematical concept for something larger than infinity) that contained the shortest, most beautiful proof for every conceivable mathematical problem. The highest compliment he could pay to a colleague’s work was to say, “That’s straight from The Book.” As for Chebyshev’s theorem, no one doubted that Erdős had found The Book proof.
— Encyclopedia Britannica

Some more of Erdös' humor can be found at