To Kesin the Horsetrainer
Kesi Sutta  (AN 4:111)

Then Kesin the horse trainer went to the Blessed One and, on arrival, having bowed down, sat to one side. As he was sitting there, the Blessed One said to him: “You, Kesin, are a trained man, a trainer of tamable horses. And how do you train a tamable horse?”

“Lord, I train a tamable horse (sometimes) with mildness, (sometimes) with harshness, (sometimes) with both mildness & harshness.”

“And if a tamable horse doesn’t submit either to a mild training or to a harsh training or to a mild & harsh training, Kesin, what do you do?”

“If a tamable horse doesn’t submit either to a mild training or to a harsh training or to a mild and harsh training, lord, then I kill it. Why is that? (I think:) ‘Don’t let this be a disgrace to my lineage of teachers.’ But the Blessed One, lord, is the unexcelled trainer of tamable people. How do you train a tamable person?”

“Kesin, I train a tamable person (sometimes) with mildness, (sometimes) with harshness, (sometimes) with both mildness & harshness.

“In using mildness, (I teach:) ‘Such is good bodily conduct. Such is the result of good bodily conduct. Such is good verbal conduct. Such is the result of good verbal conduct. Such is good mental conduct. Such is the result of good mental conduct. Such are the devas. Such are human beings.’

“In using harshness, (I teach:) ‘Such is bodily misconduct. Such is the result of bodily misconduct. Such is verbal misconduct. Such is the result of verbal misconduct. Such is mental misconduct. Such is the result of mental misconduct. Such is hell. Such is the animal womb. Such the realm of the hungry ghosts.’

“In using mildness & harshness, (I teach:) ‘Such is good bodily conduct. Such is the result of good bodily conduct. Such is bodily misconduct. Such is the result of bodily misconduct. Such is good verbal conduct. Such is the result of good verbal conduct. Such is verbal misconduct. Such is the result of verbal misconduct. Such is good mental conduct. Such is the result of good mental conduct. Such is mental misconduct. Such is the result of mental misconduct. Such are the devas. Such are human beings. Such is hell. Such is the animal womb. Such the realm of the hungry ghosts.’”

“And if a tamable person doesn’t submit either to a mild training or to a harsh training or to a mild & harsh training, what do you do?”

“If a tamable person doesn’t submit either to a mild training or to a harsh training or to a mild & harsh training, then I kill him, Kesin.”

“But it’s not proper for our Blessed One to take life! And yet the Blessed One just said, ‘I kill him, Kesin.’”

“It is true, Kesin, that it’s not proper for a Tathāgata to take life. But if a tamable person doesn’t submit either to a mild training or to a harsh training or to a mild & harsh training, then the Tathāgata doesn’t regard him as being worth speaking to or admonishing. His observant companions in the holy life don’t regard him as being worth speaking to or admonishing. This is what it means to be totally destroyed in the Dhamma & Vinaya, when the Tathāgata doesn’t regard one as being worth speaking to or admonishing, and one’s observant companions in the holy life don’t regard one as being worth speaking to or admonishing.”

“Yes, lord, wouldn’t one be totally destroyed if the Tathāgata doesn’t regard one as being worth speaking to or admonishing, and one’s observant companions in the holy life don’t regard one as being worth speaking to or admonishing?

“Magnificent, lord! 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 the Blessed One—through many lines of reasoning—made the Dhamma clear. I go to the Blessed One for refuge, to the Dhamma, and to the Saṅgha of monks. May the Blessed One remember me as a lay follower who has gone to him for refuge, from this day forward, for life.”

See also: DN 12; DN 16; MN 137; SN 6:1; SN 22:90; SN 42:7; AN 3:22; AN 4:162—163; AN 10:95