The Round of Rebirth - Samsara
An ocean of tears
"Which is greater, the tears you have shed while transmigrating & wandering this long, long time — crying & weeping from being joined with what is displeasing, being separated from what is pleasing — or the water in the four great oceans?... This is the greater: the tears you have shed... "Long have you (repeatedly) experienced the death of a mother. The tears you have shed over the death of a mother while transmigrating & wandering this long, long time — crying & weeping from being joined with what is displeasing, being separated from what is pleasing — are greater than the water in the four great oceans. "Long have you (repeatedly) experienced the death of a father... the death of a brother... the death of a sister... the death of a son... the death of a daughter... loss with regard to relatives... loss with regard to wealth... loss with regard to disease. The tears you have shed over loss with regard to disease while transmigrating & wandering this long, long time — crying & weeping from being joined with what is displeasing, being separated from what is pleasing — are greater than the water in the four great oceans. "Why is that? From an inconstruable beginning comes transmigration. A beginning point is not evident, though beings hindered by ignorance and fettered by craving are transmigrating & wandering on. Long have you thus experienced stress, experienced pain, experienced loss, swelling the cemeteries — enough to become disenchanted with all fabricated things, enough to become dispassionate, enough to be released." — Sutta Nipata XV.3
This precious human birth
"Monks, suppose that this great earth were totally covered with water, and a man were to toss a yoke with a single hole there. A wind from the east would push it west, a wind from the west would push it east. A wind from the north would push it south, a wind from the south would push it north. And suppose a blind sea-turtle were there. It would come to the surface once every one hundred years. Now what do you think: would that blind sea-turtle, coming to the surface once every one hundred years, stick his neck into the yoke with a single hole?" "It would be a sheer coincidence, lord, that the blind sea-turtle, coming to the surface once every one hundred years, would stick his neck into the yoke with a single hole." "It's likewise a sheer coincidence that one obtains the human state. It's likewise a sheer coincidence that a Tathagata, worthy & rightly self-awakened, arises in the world. It's likewise a sheer coincidence that a doctrine & discipline expounded by a Tathagata appears in the world. Now, this human state has been obtained. A Tathagata, worthy & rightly self-awakened, has arisen in the world. A doctrine & discipline expounded by a Tathagata appears in the world. "Therefore your duty is the contemplation: 'This is stress...This is the origination of stress...This is the cessation of stress...This is the path of practice leading to the cessation of stress.'" — Sutta Nipata LVI.48
Why do we wander in samsara?
"It's because of not understanding and not penetrating four things that we have wandered & transmigrated on such a long, long time, you & I. Which four? "It's because of not understanding and not penetrating noble virtue that we have wandered & transmigrated on such a long, long time, you & I. "It's because of not understanding and not penetrating noble concentration that we have wandered & transmigrated on such a long, long time, you & I. "It's because of not understanding and not penetrating noble discernment that we have wandered & transmigrated on such a long, long time, you & I. "It's because of not understanding and not penetrating noble release that we have wandered & transmigrated on such a long, long time, you & I. "But when noble virtue is understood & penetrated, when noble concentration... noble discernment... noble release is understood & penetrated, then craving for becoming is destroyed, the guide to becoming (craving & attachment) is ended, there is now no further becoming." — Anguttara Nikaya IV.1