At Savatthi. There the Blessed One said: "Monks, from an inconstruable beginning comes transmigration. A beginning point is not evident, although beings hindered by ignorance and fettered by craving are transmigrating & wandering on.
"It's just as when a dog is tied by a leash to a post or stake: If it walks, it walks right around that post or stake. If it stands, it stands right next to that post or stake. If it sits, it sits right next to that post or stake. If it lies down, it lies down right next to that post or stake.
"In the same way, an uninstructed run-of-the-mill person regards form as: 'This is mine, this is my self, this is what I am.' He regards feeling... perception... fabrications... consciousness as: 'This is mine, this is my self, this is what I am.' If he walks, he walks right around these five clinging-aggregates. If he stands, he stands right next to these five clinging-aggregates. If he sits, he sits right next to these five clinging-aggregates. If he lies down, he lies down right next to these five clinging-aggregates. Thus one should reflect on one's mind with every moment: 'For a long time has this mind been defiled by passion, aversion, & delusion.' From the defilement of the mind are beings defiled. From the purification of the mind are beings purified.
"Monks, have you ever seen a moving contraption?"
"Yes, lord."
"That moving contraption was created by the mind. And this mind is even more variegated than a moving contraption. Thus one should reflect on one's mind with every moment: 'For a long time has this mind been defiled by passion, aversion, & delusion.' From the defilement of the mind are beings defiled. From the purification of the mind are beings purified.
"Monks, I can imagine no one group of beings more variegated than that of common animals. Common animals are created by mind. And the mind is even more variegated than common animals. Thus one should reflect on one's mind with every moment: 'For a long time has this mind been defiled by passion, aversion, & delusion.' From the defilement of the mind are beings defiled. From the purification of the mind are beings purified.
"It's just as when — there being dye, lac, yellow orpiment, indigo, or crimson — a dyer or painter would paint the picture of a woman or a man, complete in all its parts, on a well-polished panel or wall, or on a piece of cloth; in the same way, an uninstructed, run-of-the-mill person, when creating, creates nothing but form... feeling... perception... fabrications... consciousness.
"Now what do you think, monks — Is form constant or inconstant?" "Inconstant, lord." "And is that which is inconstant easeful or stressful?" "Stressful, lord." "And is it fitting to regard what is inconstant, stressful, subject to change as: 'This is mine. This is my self. This is what I am'?"
"No, lord."
"...Is feeling constant or inconstant?" "Inconstant, lord."...
"...Is perception constant or inconstant?" "Inconstant, lord."...
"...Are fabrications constant or inconstant?" "Inconstant, lord."...
"What do you think, monks — Is consciousness constant or inconstant?" "Inconstant, lord." "And is that which is inconstant easeful or stressful?" "Stressful, lord." "And is it fitting to regard what is inconstant, stressful, subject to change as: 'This is mine. This is my self. This is what I am'?"
"No, lord."
"Thus, monks, any form whatsoever that is past, future, or present; internal or external; blatant or subtle; common or sublime; far or near: every form is to be seen as it actually is with right discernment as: 'This is not mine. This is not my self. This is not what I am.'
"Any feeling whatsoever...
"Any perception whatsoever...
"Any fabrications whatsoever...
"Any consciousness whatsoever that is past, future, or present; internal or external; blatant or subtle; common or sublime; far or near: every consciousness is to be seen as it actually is with right discernment as: 'This is not mine. This is not my self. This is not what I am.'
"Seeing thus, the well-instructed disciple of the noble ones grows disenchanted with form, disenchanted with feeling, disenchanted with perception, disenchanted with fabrications, disenchanted with consciousness. Disenchanted, he becomes dispassionate. Through dispassion, he is fully released. With full release, there is the knowledge, 'Fully released.' He discerns that 'Birth is ended, the holy life fulfilled, the task done. There is nothing further for this world.'"
See also: SN 22.99