According to a verbal tradition, once while Rumi was reading next to a large stack of some books, Shams Tabriz, passing by, asked Rumi, "What are you doing?" Rumi scoffingly replied, "Something you cannot understand." On hearing this, Shams threw the stack of books into a nearby pool of water. Rumi hastily took the books out of the water, but to his surprise they were all dry. Rumi then asked Shams, "What is this?" To which Shams replied, "Mowlana, this is what you cannot understand."
A second version of the tale has Shams passing by Rumi who again is reading a book. Shams, who we are given to understand Rumi regards as an uneducated stranger, asks Rumi what he is doing, to which Rumi replies, "Something that you do not understand!" At that moment, the books suddenly caught fire and Rumi asked Shams to explain what had happened. His reply was, "Something you do not understand."