When the Buddha practiced realizing the deep simplicity of all phenomena, he saw that body is empty, perception is empty, identity is empty, choice is empty, consciousness is empty; thus he overcame all ills and suffering.
And said, "My friend! Form does not differ from void, and void does not differ from form. Indeed form is void, and void is form. The same is true of feelings and numbness, creation and destruction, concern and apathy, sense and senselessness."
"My friend, void is not created or destroyed; void is not pure or impure; void is both eternal and immediate."
"Therefore, in the void there is no form, no feeling, no concept, no drive, no sense. There is no eye, no ear, no nose, no tongue, no body, no mind. There is no form, no sound, no smell, no taste, no touch, no idea. From no senses, we come to no thoughts, no ignorance, and also no end of ignorance. From no ignorance, we come to no old age and no death, and also no end of old age, and no end of death."
"Also, there is no truth in suffering, no truth in the cause of suffering, no truth in the cessation of suffering, and no truth in perfection. There is no wisdom, and there is no attainment. Because there is nothing to be attained, the enlightened man relying on the simplicity of all phenomena has no obstruction in his heart. Because there is no obstruction he has no fear, and he passes far beyond all confused imagination and reaches Nirvana."
All Buddhas in the past, present, and future have reached enlightenment by relying on the simplicity of all phenomena. Therefore, we know this simplicity is the great magic mantra, the great mantra of illumination; it is the supreme mantra, the unequaled mantra which can end all suffering."
Therefore, he spoke the mantra of the simplicity of all phenomena: "Give, give, behave, be diligent, meditate, and transcend!"
-- The Heart Sutra