By: Eihei Dogen
The Buddha says: 'When you monks unify your minds, the mind is in samadhi. Since the mind is in samadhi, you know the characteristics of the creation and destruction of the various phenomena in the world [...] When you gain samadhi, the mind is not scattered, just as those who protect themselves from floods guard the levee.
From The Eight Awarenesses of the Enlightened Person, in The Hazy Moon of Enlightenment, by Taizan Maezumi and Bernie Glassman. Dogen (1200-1253) was the founder of the Soto Zen school in Japan.