A Flower, a Rock wall, a Shout

"When Sakyamuni Buddha was at Vulture Peak, he held out a flower to his listeners. Everyone was silent. Only Kasyapa the Great broke into a broad smile. The Buddha said, 'I have the True Dharma Eye, the Marvelous Mind of Nirvana, the True Form of the Formless, and the Subtle Dharma Gate, independent of words and transmitted beyond doctrine. This I have entrusted to Kasyapa the Great.'" Mumonkan 6 .
"This is how Zen began. And this is how it was transmitted: with a flower, with a rock wall, with a shout. This approach, once it was made known by Bodhidharma and his successors, revolutionized the understanding and practice of Buddhism in China." Red Pine: xvi