This is the traditional story about the origin of Zen:
The Buddha, at one of his daily sermons on the Dharma, instead of speaking simply sat before the assembled monks and twirled a flower between his fingers. While the other Bhikkus sat, some becoming impatient for the sermon to begin, the Bhikku Mahakasyapa smiled even though he attempted to control his expression.
The Buddha noticed that smile and told the assembly: “I have the eye of the true teaching, the heart of Nirvana, the true aspect of no-form, and the ineffable stride of Dharma. Today I have passed these onto Mahakasyapa.”
[Mahakasyapa – Zen Masters of China, pages 25-26]