[443] On one occasion the Blessed One was dwelling at Sāvatthī … There the Blessed One … [said:] "Bhikkhus, this round of rebirths (saṃsāra) is without discoverable beginning. A first point is not evident of beings who, hindered by ignorance (avijjā) and fettered by craving (taṇhā), run on and wander on. Bhikkhus, when you see anyone unfortunate and ill-favoured, you should come to the conclusion in that case: 'We too have experienced such a thing in this long course of time.' For what reason? Bhikkhus, this saṃsāra is without discoverable beginning … enough to be liberated." The first [sutta].
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.