At Sāvatthi.

"Bhikkhus, this cyclic existence is without a discoverable beginning. A first point is not discerned for beings who, obstructed by ignorance and fettered by craving, run on and wander in this cycle of existence.

Suppose, bhikkhus, a man were to reduce this great earth to small clay balls, each the size of a jujube kernel, and scatter them, marking each one: 'This one is my father; this one is my father's father,' and so on. Even so, bhikkhus, the sequence of that man's fathers would still remain incomplete before this great earth was completely exhausted and used up.

For what reason? Bhikkhus, this cyclic existence is without a discoverable beginning. A first point is not discerned for beings who, obstructed by ignorance and fettered by craving, run on and wander in this cycle of existence. For such a long time, bhikkhus, you have experienced suffering, agony, and calamity, the cemetery has been filled up with your bones. Therefore, bhikkhus, it is enough to become disenchanted, to become detached and to become free from all conditions."