Zen sayings or koans belong to a school of Mahayana Buddhism (though this point is contested by some) that came to be known as Chan (derivative of dhyana in Sanskrit) in China in the 6th century before it spread out to Korea and Japan.
Zen has been called anti-intellectual, as it de-emphasizes religious doctrine and theoretical knowledge in favor of direct experiential wisdom.
Zen sayings serve as a medium for zen masters to communicate the importance of insight and personal expression and the futility of knowledge and over-intellectualization on the path to awakening and enlightenment.
Here are some of my personal favorites:
"If you want to climb a mountain, begin at the top"
"When you get to the top of the mountain, keep climbing"
"Where there is great doubt, there will be great awakening; small doubt, small awakening, no doubt, no awakening"
"If you do not get it from yourself, where will you go for it?"
"The frog in the pond knows little of the great ocean"
"When I eat, I eat; when I sleep, I sleep"
"To cry and not be carried away by tears, to laugh and not be carried away by laughter, is the way"
"If you understand, things are just as they are; if you do not understand, things are just as they are"
"The greater the passion, the greater the Buddha"
"Before enlightenment, I chopped wood and carried water. After enlightenment, I chopped wood and carried water"
"The instant you speak about a thing, you miss the mark"
"What is inexpressible is inexhaustible in its use"
"Therefore the Three Realms are only mind"
"One moon shows in every pool, in every pool the one moon"
"Not thinking of good, not thinking of evil - tell me, what was your original face before your mother and father were born?"
"When you pass through, no one can pin you down, no one can call you back"
"To study the way of the Buddha is to study oneself. To study oneself is to forget oneself. To forget oneself is to be enlightened by everything"
"If you wish to know the taste of seawater and you live on an island, set out towards the coast and keep going. When you reach the seashore all you then need to do is to bend down, put the finger into the water, and then into the mouth and you will know the taste of all the seven seas. So it is with freedom, it has but one single taste" - Rinzai Zen Master Hakuin
"Many have come to realization simply by listening to the tinkling of a bell or some other sound" - Roshi Philip Kapleau
"You should stop pursuing words and letters, and learn to withdraw and reflect on yourself. When you do so, your body and mind will fall away naturally and your original Buddha-nature will appear" - Dogen
"In the scenery of spring, nothing is better, nothing worse; The flowering branches are; some long, some short" - Eicho
"Sitting quietly doing nothing, spring comes, grass grows of itself" - Eicho
"If we look at the world with a deluded body and mind, we will think that our self is permanent. But if we practice correctly and return to our true self, we will realize that nothing is permanent" - Dogen
"The Great Way is not difficult, it only avoids picking and choosing" - Sosan
"Zen is not some kind of excitement, but concentration on our usual everyday routine" - Shunryu Suzuki
"When you forget the good and the non-good, the worldly life and the religious life, and all other dharmas, and permit no thoughts relating to them to arise, and you abandon body and mind—then there is complete freedom. When the mind is like wood or stone, there is nothing to be discriminated" - Pai-chang Huai-hai
"I would rather sink to the bottom of the sea for endless eons than seek liberation through all the saints of the universe" - Shih-t'ou
"Keep your mind alive and free without abiding in anything or anywhere" - Diamond Sutra
"Do not mistake understanding for realization, and do not mistake realization for liberation" - Tibetan saying
"Do not seek to follow in the footsteps of the men of old; seek what they sought" - Basho
"The whole moon and the entire sky are reflected in one dewdrop on the grass" - Dogen
"The fundamental delusion of humanity is to suppose that I am here and you are out there" - Yasutani Roshi
I hope the zen sayings above either unlock the door to some mystery you find worth pursing or help in bringing some bright new insight to you.
Remember that meditation is as much about sitting still, as it is about regularly contemplating the truths espoused in zen sayings or other enlightenment/buddhist quotes outside of the sitting hours.
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