The Platform Sutra tells it as a contest. The Fifth Patriarch, looking for a successor, asks his monks to write a verse showing what they have understood. The head monk Shenxiu writes on the corridor wall that the body is the tree of awakening and the mind a bright mirror stand, which must be polished constantly so that no dust settles on it. It is a good verse and everyone says so.
Huineng, in the story an illiterate southerner working in the kitchen pounding rice, hears it read out and asks someone to write his reply beside it. There is no tree of awakening and no mirror stand; since from the beginning not one thing exists, where could dust alight. The patriarch, seeing which of the two has grasped it, rubs the verse off the wall so that nobody will make trouble, calls Huineng in at night, transmits the teaching and the robe, and sends him south before dawn because the monks will kill him for it.
This is the founding narrative of a school, and it should be read as one. It is the story the Southern tradition told about itself in the eighth century, and the historical Huineng behind it is a shadowy figure of whom very little independent is known. What the narrative was designed to establish is the doctrinal point: that awakening is not a cleaning process carried out over years on a mind conceived as a surface, but the recognition that there was never a surface.