The Awakening of Buddha
The Bodhisattva had triumphed over Mara. The full moon rose in the sky. The Bodhisattva, unmoving, entered into the first level of meditation. The night was utterly silent. As the moon continued to rise, the Bodhisattva's composure deepened, and one by one he mastered the levels of meditation until he reached the fourth. His concentration was bright and unblemished, full and balanced. Then through great confidence and trust, he relinquished the watcher, and his mind entered into a fathomless openness untroubled by content. Here the Bodhisattva naturally rested until a profound contentment pervaded him. But as one who already knew the way, he did not become caught up in this. Rather, with utter clarity and tenderness, he turned his mind to untying the knot of birth, old age, sickness, and death.
He saw that the condition for old age, sickness, and death is birth. He saw that the condition for birth lay in processes of becoming already set in motion; that the condition for this was grasping or craving; that the condition for this was desire; and the condition for desire, feelings of happiness, suffering, or indifference, and the condition for these, sensual contact; and the condition for sensual contact, the fields of the senses; the condition for sense fields, the arising of mind-body; the condition for mind-body, consciousness. He saw that mind-body and consciousness conditions each other to make a rudimentary sense of self. He saw that the condition for consciousness was volitional impulses, and finally that the conditions for them was ignorance.
Thus he saw that the whole process ending in old age and death begins when basic intelligence slips into unawareness of its own nature. In this way all-pervading intelligence strays into the sense of a self.
After the Bodhisattva had penetrated the nature of the process of birth, old age, sickness, and death, the clarity and openness of his mind increased. His inner vision became completely unobstructed. This is called the opening of the divine eye. Then he turned his attention to the past, and saw his and others' countless past lives.
Then, moved by compassion, he opened his wisdom eye further and saw the spectacle of the whole universe as in a spotless mirror. He saw beings born and passing away in accordance with karma, the laws of cause and effect. Just as, when one clears one's throat, one is next ready to speak, past deeds create a certain inclination. When the basic condition of ignorance is present, the inclination takes shape in a kind of volitional impulses, which engender a consciousness, and so on up to old age and death, and then once more into ignorance and volitional impulses. Seeing birth and death occurring in accordance with this chain of causality, the Bodhisattva saw the cyclic paths of all beings. He saw the fortunate and the unfortunate, the exalted and the lowly going their various ways.
Then he applied himself to rooting out this suffering once and for all. He had clearly understood the wheel of dependent arising in which each stage follows from a preceding cause, beginning with ignorance. And he saw how beings were driven on it by the powerful motive force of karma. He saw that through the cessation of birth, old age and death would not exist, through the cessation of becoming, there would be no birth; through the cessation of grasping, no becoming-and so back through the sequence of causation to ignorance. He saw suffering, the cause of suffering, the cessation of suffering, and at last also the path to cessation.
At first light of dawn the Bodhisattva saw through the very trace of ignorance in himself. Thus he attained complete and utter enlightenment and became the Buddha.
(A compilation from the Pali Canon, the Lalitavishtara Sutra, and the Buddhacharita)
Original story here