Buddhist Sutra meaning The Discourse on the Establishing of Mindfulness , Fundamental Teaching of Buddha
"Satipatthana Sutta - The Foundation of Mindfulness Translated from Pali: A monk lives contemplating the body in the body, ardent, clearly comprehending and mindful, having overcome, in this world, covetousness, and grief; he lives contemplating feelings in feelings, ardent, clearly comprehending and mindful, having overcome, in this world, covetousness and grief; he lives contemplating consciousness in consciousness, ardent, clearly comprehending and mindful, having overcome, in this world, covetousness and grief; he lives contemplating mental objects in mental objects, ardent, clearly comprehending and mindful, having overcome, in this world, covetousness and grief."
"He searches all around for his thought. But what thought? It is either passionate, or hateful, or confused. What about the past, future or present? What is past that is extinct, what is future that has not yet arrived, and the present has no stability. For thought, Kasyapa, cannot be apprehended, inside, or outside, or in between both. For thought is immaterial, invisible, nonresisting, inconceivable, unsupported, and homeless. Thought has never been seen by any of the Buddhas, nor do they see it, nor will they see it. And what the Buddhas never see, how can that be an observable process, except in the sense that dharmas proceed by the way of mistaken perception? Thought is like a magical illusion; by an imagination of what is actually unreal it takes hold of a manifold variety of rebirths. A thought is like the stream of a river, without any staying power; as soon as it is produced it breaks up and disappears. A thought is like a flame of a lamp, and it proceeds through causes and conditions. A thought is like lightning, it breaks up in a moment and does not stay on... Can thought review thought? No, thought cannot review thought. As the blade of a sword cannot cut itself, so a thought cannot see itself. Moreover, vexed and pressed hard on all sides, thought proceeds, without any staying power, like a monkey or like the wind. It ranges far, bodiless, easily changing, agitated by the objects of sense, with the six sense-fields for its sphere, connected with one thing after another. The stability of thought, its one-pointedness, its immobility, its undistraughtness, its one-pointed calm, its nondistraction, that is on the other hand called mindfulness as to thought."