​MN 57 Kukkuravatika Sutta: The Dog-duty Ascetic 

Thus have i heard.

On one occasion the Blessed One was living in the Koliyan country at a town of the Koliyans named Haliddavasana. Then Punna, son of the Koliyans, an ox-duty ascetic (behave like an ox), and also Seniya, a naked dog-duty ascetic (behave like a dog), went to the Blessed One. Punna, the ox-duty ascetic, paid homage to the Blessed One and sat down at one side, while Seniya, the naked dog-duty ascetic, exchanged greetings with the Blessed One, and when this courteous and amiable talk was finished, he too sat down at one side curled up like a dog.

Punna, the ox-duty ascetic, said to the Blessed One: "Venerable sir, this Seniya is a naked dog duty ascetic who does what is hard to do: he eats his food when it is thrown to the ground. He has long taken up and practised that dog-duty. What will be his destination? What will be his future course?"
Buddha: "Enough, Punna, let that be. Do not ask me that."
A second time...And a third time Punna, the ox-duty ascetic, said to the Blessed One: "Venerable sir, this Seniya is a naked dog-duty ascetic , What will be his destination? What will be his future course?"

Buddha: "Well, Punna, since I certainly cannot persuade you when I say: 'Enough, Punna, let that be. Do not ask me that,' I shall therefore answer you.
"Here, Punna, someone develops the dog-duty fully and uninterruptedly; he develops the dog-habit fully and uninterruptedly; he develops the dog-mind fully and uninterruptedly; he develops dog-behaviour fully and uninterruptedly. Having done so, on the dissolution of the body, after death, he reappears in the company of dogs. But if he has such a view as this: 'By this virtue or observance or asceticism or holy life living like a dog, I shall become a great god or some lesser god: that is wrong view in his case. Now there are two destinations for one with wrong view, I say: hell or the animal realm. So, Punna, if his dog-duty succeeds, it will lead him to the company of dogs; if it fails, it will lead him to hell." 

​ When this was said, Seniya the naked dog-duty ascetic cried out and burst into tears. Then the Blessed One told Punna, son of the Koliyans, the ox-duty ascetic: "Punna, I could not persuade you when I said: 'Enough, Punna, let that be. Do not ask me that"
Then Seniya the naked dog-duty ascetic said: "Venerable sir, I am not crying because the Blessed One has said this about me, but because I have long taken up and practised this dog-duty. Venerable sir, this Punna, son of the Koliyans, is an ox-duty ascetic. He has long taken up and practised that ox-duty. What will be his destination? What will be his future course?"
Buddha:"Enough, Seniya, let that be. Do not ask me that."
A second time...And a third time Seniya the naked dog-duty ascetic asked the Blessed One: "Venerable sir, this Punna, son of the Koliyans, is an ox-duty ascetic. He has long taken up and practised that ox-duty. What, will be his destination? What will be his future course?"

Buddha: "Well, Seniya, since I certainly cannot persuade you when I say: 'Enough, Seniya, let that be. Do not ask me that I shall therefore answer you."
"Here, Seniya, someone develops the ox-duty fully and uninterruptedly; he develops the ox-habit fully and uninterruptedly; he develops the ox-mind fully and uninterruptedly; he develops ox-behaviour fully and uninterruptedly. Having done so, on the dissolution of the body, after death, he reappears in the company of oxen. But if he has such a view as this: 'By this virtue or observance or asceticism or holy life living like an ox I shall become a great god or some lesser god,' that is wrong view in his case. Now there are two destinations for one with wrong view, I say: hell or the animal realm. So, Seniya, if his ox-duty succeeds, it will lead him to the company of oxen; if it fails, it will lead him to hell."

When this was said, Punna, son of the Koliyans, the ox-duty ascetic cried out and burst into tears. Then the Blessed One told Seniya the naked dog-duty ascetic: "Seniya, I could not persuade you when I said: 'Enough, Seniya, let that be. Do not ask me that.'" 

Then Punna the ox-duty ascetic said: "Venerable sir, I am not crying because the Blessed One has said this about me, but because 1 have long taken up and practised this ox-duty. Venerable sir, I have confidence in the Blessed One thus: 'The Blessed One is capable of teaching me the Dhamma in such a way that I can abandon this ox-duty and that this Seniya the naked dog-duty ascetic can abandon that dog-duty.'"
Buddha: "Then, Punna, listen and attend closely to what I shall say."
"Yes, venerable sir," he replied.

The Blessed One said this: "Punna, there are four kinds of action proclaimed by me after realizing them for myself with direct knowledge. What are the four?
1. There is dark action with dark result
2. There is bright action with bright result
3. There is dark-and-bright action with dark-and-bright result
4. There is action that is neither dark nor bright with neither-dark-nor-bright result
action that leads to the destruction of action.

"And what, Punna, is dark action with dark result? Here someone generates an hurtful bodily formation, an hurtful verbal formation, an hurtful mental formation. Having generated hurtful choices by way of body, speech and mind, he reappears in an afflictive world. When he has reappeared in an afflictive world, hurtful contacts touch him. Being touched by hurtful contacts, he feels afflictive feelings, extremely painful, as in the case of the beings in hell. Thus a being's reappearance is due to a being: one reappears through the actions one has performed. When one has reappeared, contacts touch one. Thus I say beings are the heirs of their actions. This is called dark action with dark result. "

"And what, Punna, is bright action with bright result? Here someone generates a pleasing bodily formation, a pleasing verbal formation, a pleasing mental formation. Having made pleasing choices by way of body, speech and mind, he reappears in a pleasing world. When he has reappeared in a pleasing world, pleasing contacts touch him. Being touched by pleasing contacts, he feels pleasing feelings, extremely pleasant, as in the case of the gods of Refulgent Glory. Thus a being's reappearance is due to a being; one reappears through the actions one has performed. When one has reappeared, contacts touch one. Thus I say beings are the heirs of their actions. This is called bright action with bright result. "

​ "And what, Punna, is dark-and-bright action with dark and-bright result? Here someone generates a bodily formation that is both hurting and pleasing, a verbal formation that is both  hurting and pleasing, a mental formation that is both  hurting and pleasing. Having generated a bodily formation, a verbal formation, a mental formation that is both  hurting and pleasing, he reappears in a world that is both hurtful and pleasing. When he has reappeared in a world that is both hurtful and pleasing, both hurtful and pleasing contacts touch him. Being touched by both hurtful and pleasing contacts, he feels both hurtful and pleasing feelings, mingled pleasure and pain, as in the case of human beings and some gods and some beings in the lower worlds. Thus a being's reappearance is due to a being: one reappears through the actions one has performed. When one has reappeared, contacts touch one. Thus I say beings are the heirs to their actions. This is called dark-and-bright action with dark-and-bright result."

"And what, Punna, is action that is neither dark nor bright with neither-dark-nor-bright result, action that leads to the destruction of action? Therein, the volition in abandoning the kind of action that is dark with dark result, and the volition in abandoning the kind of action that is bright with bright result, and the volition in abandoning the kind of action that is dark and bright with dark-and-bright result: this is called action that is neither dark nor bright with neither-dark-nor-bright result, action that leads to the destruction of action.
These are the four kinds of action proclaimed by me after realising them for myself with direct knowledge."

When this was said, Punna, son of the Koliyans, the ox-duty ascetic said to the Blessed One: "Magnificent, venerable sir! Magnificent, venerable sir! The Blessed One has made the Dhamma clear in many ways. From today let the Blessed One remember me as a lay follower who has gone to him for refuge for life."

But Seniya the naked dog-duty ascetic said to the Blessed One: "Magnificent, venerable sir! Magnificent, venerable sir! The Blessed One has made the Dhamma clear in many ways, as though he were turning upright what had been overthrown, revealing what was hidden, showing the way to one who was lost, or holding up a lamp in the dark for those with eyesight to see forms. I go to the Blessed One for refuge and to the Dhamma and to the Sangha of bhikkhus. I would receive the going forth under the Blessed One, I would like t o ordain into the order." 

 "Seniya, one who formerly belonged to another sect and desires the going forth and the full admission in this Dhamma and Discipline need to go through a probation for four months. At the end of four months, if the bhikkhus are satisfied with him, they give him the going forth and the full admission to the bhikkhus' state. But I recognize individual differences in this matter."

Seniya: "Venerable sir, if those who formerly belonged to another sect and desire the going forth and the full admission in this Dhamma and Discipline live on probation for four months, and if at the end of the four months the bhikkhus being satisfied with them give them the going forth and the full admission to the bhikkhus' state, then I will live on probation for four years. At the end of the four years if the bhikkhus are satisfied with me, let them give me the going forth and the full admission to the bhikkhus' state."

Then Seniya the naked dog-duty ascetic received the going forth under the Blessed One, and he received the full admission. And soon, not long after his full admission, dwelling alone, withdrawn, diligent, ardent, and resolute, the venerable Seniya, by realizing for himself with direct knowledge, here and now entered upon and abide in that supreme goal of the holy life for the sake of which clansmen rightly go forth from the home life into homelessness. He directly knew: "Birth is destroyed, the holy life has been lived, what had to be done has been done, there is no more coming to any state of being." And the venerable Seniya became one of the arahants. 

​In summary, the Buddha meets two ascetics (punna and seniya) who undertook extreme practices, such as a vow to behave like an ox or a dog.  Buddha was reluctantly pressed to reveal the kammic outcomes of such practice. In answer to their persistent questioning, the Buddha says that the future reborn state of one who practice in such a way is either purgatory or rebirth as an animal (among cattle and dogs respectively). He then proceeded to give them a discourse on kamma and its fruit. 

• (1) Dark, with dark outcome;
• (2) bright, with bright outcome;
• (3) both dark and bright with similar outcome; and
• (4) neither dark nor bright with corresponding outcome.

After the discourse, both Punna and Seniya were delighted in the teaching and took refuge in the Buddha. Seniya entered the monks order and later achieved arahantship. 

​References: 
1. www.accesstoinsight.org
2. https://suttacentral.net/
3. The middle length discourses of the Buddha (Bhikkhu Bodhi)