SN 15.12
CDB i 658
Sukhita Sutta: Happy
translated from the Pali by
Thanissaro Bhikkhu

At Savatthi . There the Blessed One said: "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. When you see someone who is happy & well-provided in life, you should conclude: 'We, too, have experienced just this sort of thing in the course of that long, long time.'

"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."