Rowen's precious books refer to imperial books and imperial books; Tianfa Oracle is a monument carved in Wu Dong during the Three Kingdoms period. It is said to be the work of calligrapher Yu Xiang, and now it is in Nanjing Museum.
The two couplets imply that the emperor's treasure books are omniscient (there is no forbidden book), and the tablet of "the divinity of God" is specially used to make predictions.