The Ganges
Gangā Sutta  (SN 15:8)

On one occasion the Blessed One was staying near Rājagaha, in the Bamboo Forest, the Squirrels’ Sanctuary. Then a certain brahman went to the Blessed One and, on arrival, exchanged courteous greetings with him. After an exchange of friendly greetings & courtesies, he sat to one side. As he was sitting there he said to the Blessed One, “How many eons, Master Gotama, have passed and gone by?”

“Many eons, brahman, have passed and gone by. They are not easy to count: ‘So many eons have passed and gone by’ or ‘So many hundreds of eons have passed and gone by’ or ‘So many thousands of eons have passed and gone by’ or ‘So many hundreds of thousands of eons have passed and gone by.’”

“But is it possible to give an analogy, Master Gotama?”

“It is, brahman,” the Blessed One said. “Just as, from where the River Ganges begins to where it goes to the ocean, the grains of sand in between are not easy to count as ‘so many grains of sand’ or ‘so many hundreds of grains of sand’ or ‘so many thousands of grains of sand’ or ‘so many hundreds of thousands of grains of sand.’ Even more than that are the eons that have passed and gone. They are not easy to count: ‘So many eons have passed and gone by’ or ‘So many hundreds of eons have passed and gone by’ or ‘So many thousands of eons have passed and gone by’ or ‘So many hundreds of thousands of eons have passed and gone by.’

“Why is that? From an inconceivable beginning comes the wandering-on, brahman. A beginning point is not discernible, 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 fabrications, enough to become dispassionate, enough to be released.”

When this was said, the brahman said to the Blessed One, “Magnificent, Master Gotama! Magnificent! Just as if he were to place 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 has Master Gotama—through many lines of reasoning—made the Dhamma clear. I go to Master Gotama for refuge, to the Dhamma, & to the Saṅgha of monks. May Master Gotama remember me as a lay follower who has gone for refuge from this day forward, for life.”