This is how I heard. At one time, the Blessed One was living at the city of Rājagaha, in the Bamboo Garden, at the Squirrel Park. Then, a certain man of the brahmin caste approached the Blessed One, and exchanged greetings with him. After their greetings and friendly talk, the man sat down to one side and said to the Buddha, “Master Gotama, how many eons have passed by and gone by?”
“Brahmin, many eons have passed by and gone by. It is not easy to count them and say there are so many eons, or so many hundreds of eons, or so many thousands of eons, or so many hundreds of thousands of eons.”
“But, Master Gotama, is it possible to give a simile to know how many eons have passed by and gone by?”
“It is possible, brahmin,” The Blessed One said, “Brahmin, let us think about the amount of grains of sand between the point where the river Gaṅgā starts and the point where it enters the great ocean. It is not easy to count them and say there are so many grains of sand, so many hundreds of grains, so many thousands of grains, or so many hundreds of thousands of grains.
“Brahmin, the amount of eons that have passed by and gone by are even greater than that. It is not easy to count them and say that there are so many eons, so many hundreds of eons, so many thousands of eons, or so many hundreds of thousands of eons. What is the reason for that? It is because, brahmin, this cycle of rebirth is endless. The beginning of this extremely long journey cannot be discovered. These beings, hindered by lack of knowledge of the true nature of life and bound by craving, roam and wander on in this endless journey.
“For such a long time, brahmin, you have experienced various types of suffering, tragedies, and disasters. You have filled the cemetery with your dead bodies. Therefore, brahmin, the time has come for you to understand the meaningless nature of all conditioned things; the time has come for you to become detached from them; and the time has come for you to be liberated from them.”
When the Buddha taught this discourse, that brahmin said to the Blessed One, “It is wonderful, Master Gotama! It is excellent, Master Gotama! Just as a man were to set upright what was overturned, to reveal what was hidden, to show the way to one who was lost, or to carry a lamp into the dark so that those with eyes could see forms, in the same way, the Dhamma has been made clear in many ways by the Master Gotama. I go for refuge to the Master Gotama, to the Dhamma, and to the community of monks. Master Gotama, from today, please accept me as a lay follower who has gone for refuge to the Buddha, the Dhamma, and the Sangha for life.”