All Zen students are instructed to devote themselves to the practice of za-zen. 'Sitting' (za) means not pushing, pulling, introspecting, interrogating, analyzing, or litigating with thoughts, abiding in the mind. 'Zen' means remaining undisturbed internally as you notice and see your authentic-nature. This seems to me a clear and succinct definition of zazen.
Sitting in either the full lotus position or the half-lotus position, with the eyes half-shut, see the Original face which was before your father or mother was born. This means to see the state before the parents were born, before heaven and earth were parted, before you received human form. What is called the Original face will appear. That Original face is something without color or form, like the empty sky in whose clarity there is no form.
The Original face is really nameless, but it is indicated by such terms as Original face, Master, The Source, Original nature, the Tao, Universal Identity of Loving Presence, Buddha nature, or That One shining alone. It is as with man, who has no name at birth, but afterwards various names are attached to him. The seventeen hundred koan or themes to which Zen students devote themselves are all only for making them see their Original face. The World-honoured One sat in meditation in the snowy mountains for six years, then saw the morning star and was enlightened, and this was seeing his Original face. When it is said of others of the ancients that they had a great realization, or a great breaking-through, it means they saw the original face. The Second Patriarch stood in the snow and cut off his arm to get realization; the Sixth Patriarch heard the phrase from the Diamond Sutra and was enlightened. Reiun was enlightened when he saw the peach blossoms, Kyogen on hearing the tile hit the bamboo, Rinzai when struck by Obaku, Tozan on seeing his own reflection in the water.
All this is what is called "meeting Universal Identity of Loving Presence or Master," through directly noticing what is always right here and right now, yet somehow missed though in plain sight. The body is a house, and it must have a Master. It is the Master of the house who is known as the Original face. Experiencing heat and cold and so on, or feeling a lack, or having desires--these are all delusive thoughts and do not belong to the True Master of the house. These delusive thoughts are something added. They are things which vanish with each breath. To be dragged along by them is to fall into delusion, walking in circles re-enacted out of habit energy. By going deeper and deeper into zazen, that thoughts have no True source. They are ghosts haunting the body as thought. A thought is something without any form or body, but owing to the conviction of those thoughts remaining even after death, people fall into delusion with its many pains, or suffers in the round of this changing world.
Every time a thought arises, do not try to hold on to the flickering projections of mind, turning it into what it is not. Just devote yourself to sweeping away the thoughts. Sweeping away thoughts means performing zazen. When thought is put down, the Original face appears. The thoughts are like clouds; when the clouds have cleared, the moon appears. That moon of eternal truth is the Original face.
There has never been a moment we have not been Buddha, Universal Identity of Loving Presence, only moments of being distracted away by thought. What is called "seeing one's nature" means to realize our True Identity. Again and again, we renew our practice of not holding onto thoughts, noticing our inherent Buddha nature that is here and now, without distance.
It might be supposed from this that the True nature will not be visible except when sitting in meditation. That is a mistake. Yoka Daishi says: "Standing is Zen, walking is Zen, laying down and resting is Zen. Speaking or silent, moving the body or still, Buddha is Buddha." This teaches that going and sitting and talking are all Zen. Zazen is NOT suppressing the thoughts. Zazen is NOT catering to their appearance. Whether rising or sitting, maintain remain unmoved, yet alert. All of a sudden, the Original face will confront you, and you well realize your own feet.
一Daitō Kokushi | 大燈国師