​MN 90 Kannakatthala Sutta: At Kannakatthala 

 Thus have i heard.

On one occasion the Blessed One was living at Ujuftna, in the Kannakatthala Deer Park. 2. Now on that occasion King Pasenadi of Kosala had arrived at Ujunna for some business or other. Then he told a man: "Come, good man, go to the Blessed One and pay homage in my name with your head at his feet, and ask whether he is free from illness and affliction, and is healthy, strong, and abiding in comfort, saying: 'Venerable sir, King Pasenadi of Kosala pays homage with his head at the Blessed One's feet, and he asks whether the Blessed One is free from illness...and abiding in comfort.' And say this: 'Venerable sir, today King Pasenadi of Kosala will come to see the Blessed One after he has had his breakfast.'" "Yes, sire," the man replied, and he went to the Blessed One, and after paying homage to him, he sat down at one side and delivered his message.

The sisters Soma and Sakula845 heard: "Today King Pasenadi of Kosala will go to see the Blessed One after he has had his breakfast." Then, while the meal was being served, the two sisters went to the king and said: "Sire, pay homage in our name with your head at the Blessed One's feet, and ask whether he is free from illness...and abiding in comfort, saying: 'Venerable sir, the sisters Soma and Sakula pay homage with their heads at the Blessed One's feet, and they ask whether he is free from illness.. .and abiding in comfort."'

Then, when he had finished his breakfast, King Pasenadi of Kosala went to the Blessed One, and after paying homage to him, he sat down at one side and delivered the message of the sisters Soma and Sakula. 

Buddha: "But, great king, could the sisters Soma and Sakula find no other messenger?"
King: "Venerable sir, the sisters Soma and Sakula heard: 'Today King Pasenadi of Kosala will go to see the Blessed One after he has had his breakfast.' Then, while the meal was being served, the sisters Soma and Sakula came to me and said: 'Sire, pay homage in our names with your head at the Blessed One's feet, and ask whether he is free from illness.. .and abiding in comfort.'" 

Buddha: "May the sisters Soma and Sakula be happy, great king."

Then King Pasenadi of Kosala said to the Blessed One: "Venerable sir, I have heard this: 'The recluse Gotama says: "There is no recluse or brahmin who is omniscient and all-seeing, who can claim to have complete knowledge and vision; that is not possible.'" Venerable sir, do those who speak thus say what has been said by the Blessed One, and not misrepresent him with what is contrary to fact? Do they explain in accordance with the Dhamma in such a way that nothing that provides a ground for censure can be legitimately deduced from their assertions?"

Buddha: "Great King, those who speak thus do not say what has been said by me, but misrepresent me with what is untrue and contrary to fact." Then King Pasenadi of Kosala addressed General Vidudabha: "General, who introduced this story into the palace?" The general replied: "It was Sanjaya, sire, the brahmin of the Akasa clan."

Then King Pasenadi of Kosala told a man: "Come, good man, in my name tell Sanjaya, the brahmin of the Akasa clan: 'Venerable sir, King Pasenadi of Kosala calls you.'" "Yes, sire," the man replied. He went to Sanjaya, the brahmin of the Akasa clan, and told him: "Venerable sir, King Pasenadi of Kosala calls you." Meanwhile King Pasenadi of Kosala said to the Blessed One: "Venerable sir, could something else have been said by the Blessed One referring to that, and the person understood it wrongly? In what way does the Blessed One recall making that utterance?"

Buddha: "I recall having actually made the utterance in this way, great king: 'There is no recluse or brahmin who knows all, who sees all, simultaneously; that is not possible.'"
King: "What the Blessed One has said appears reasonable, what the Blessed One has said appears to be supported by reason: 'There is no recluse or brahmin who knows all, who sees all, simultaneously; that is not possible.'" 

King: "There are these four castes, venerable sir: the nobles, the brahmins, the merchants, and the workers. Is there any distinction or difference among them?"
Buddha: "There are these four castes, great king: the nobles, the brahmins, the merchants, and the workers. Two of them, that is, the nobles and the brahmins, are held to be superior since men pay homage to them, rise up for them, and accord them reverential salutation and polite services."

King: "Venerable sir, I was not asking about this present life; I was asking about the life to come. There are these four castes, venerable sir: the nobles, the brahmins, the merchants, and the workers. Is there any distinction or difference among them?"

Buddha: "Great king, there are these five factors of striving. What five? Here a bhikkhu has faith, he places his faith in the Tathagata's enlightenment thus: 'The Blessed One is accomplished, fully enlightened, perfect in true knowledge and conduct, sublime, knower of worlds, incomparable leader of persons to be tamed, teacher of gods and humans, enlightened, blessed.' Then he is free from illness and affliction, possessing a good digestion that is neither too cool nor too warm but medium and able to bear the strain of striving. Then he is honest and sincere, and shows himself as he actually is to his teacher and his companions in the holy life. Then he is energetic in abandoning unwholesome states and in undertaking wholesome states, steadfast, launching his effort with firmness and persevering in cultivating wholesome states. Then he is wise; he possesses wisdom regarding rise and disappearance that is noble and penetrative and leads to the complete destruction of suffering. These are the five factors of striving. "There are these four castes, great king: the nobles, the brahmins, the merchants, and the workers. Now if they possessed these five factors of striving, it would lead to their welfare and happiness for a long time."

King:"Venerable sir, there are these four castes: the nobles, the brahmins, the merchants, and the workers. Now if they possessed these five factors of striving, would there be any difference among them here in that respect?" 

Buddha: "Here, great king, I say that the difference among them would lie in the diversity of their striving. Suppose there were two tamable elephants or tamable horses or tamable oxen that were well tamed and well disciplined, and two tamable elephants or tamable horses or tamable oxen that were untamed and undisciplined. What do you think, great king? Would the two tamable elephants or tamable horses or tamable oxen that were well tamed and well disciplined, being tamed, acquire the behaviour of the tamed, would they arrive at the grade of the tamed?"
King: "Yes, venerable sir."
Buddha: "And would the two tamable elephants or tamable horses or tamable oxen that were untamed and undisciplined, being untamed, acquire the behaviour of the tamed, would they arrive at the grade of the tamed, like the two elephants or horses or oxen that were well tamed and well disciplined?"
King: "No, venerable sir."

Buddha: "So too, great king, it is not possible that what can be achieved by one who has faith, who is free from illness, who is honest and sincere, who is energetic, and who is wise, can be achieved by one who has no faith, who has much illness, who is fraudulent and deceitful, who is lazy, and who is not wise."
King:  "What the Blessed One has said appears reasonable, what the Blessed One has said appears to be supported by reason. "There are these four castes, venerable sir: the nobles, the brahmins, the merchants, and the workers. Now if they possessed these five factors of striving, and if their striving was right, would there be any difference among them in that respect?"

Buddha: "Here, great king, in this respect I say that among them there is no difference, that is, between the deliverance of one and the deliverance of the others. Suppose a man took dry saka wood, lit a fire, and produced heat; and then another man took dry sala wood, lit a fire, and produced heat; and then another man took dry mango wood, lit a fire, and produced heat; and then another man took dry fig wood, lit a fire, and produced heat. What do you think, great king? Would there be any difference among these fires lit with different kinds of wood, that is, between the flame of one and the flames of the others, or between the color of one and the colours of the others, or between the radiance of one and the radiances of the others?" 

​King: "No, venerable sir."
Buddha: "So too, great king, when a fire is kindled by energy, lit by striving, there is, I say, no difference, that is, between the deliverance of one and the deliverance of the others."
King: "What the Blessed One has said appears reasonable, what the Blessed One has said appears to be supported by reason. But, venerable sir, how is it: are there gods?"

Buddha: "Why do you ask that, great king?"
King: "Venerable sir, I was asking whether those gods come back to this human state or whether they do not." Buddha: "Great king, those gods who are still subject to affliction come back to this human state, those gods who are no longer subject to affliction do not come back to this human state."

When this was said, General Vidudabha asked the Blessed One: "Venerable sir, can those gods who are still subject to affliction and who come back to this human state topple or banish from that place those gods who are no longer subject to affliction and who do not come back to this human state?"
Then the venerable Ananda thought: "This General Vidudabha is the son of King Pasenadi of Kosala, and I am the son of the Blessed One. This is the time for one son to talk with the other."
He said to General Vidudabha: "General, I shall ask you a question in return. Answer it as you choose. General, what do you think? There is the whole extent of King Pasenadi of Kosala's realm, where he exercises lordship and sovereignty; now can King Pasenadi of Kosala topple or banish from that place any recluse or brahmin, irrespective of whether that recluse or brahmin has merit or not and whether he leads the holy life or not?"
General: "He can do so, sir."

Ven Ananda: "What do you think, general? There is the whole extent that is not King Pasenadi of Kosala's realm, where he does not exercise lordship and sovereignty; now can King Pasenadi of Kosala topple or banish from that place any recluse or brahmin, irrespective of whether that recluse or brahmin has merit or not and whether he leads the holy life or not?"
General: "He cannot do so, sir."
Ven Ananda: "General, what do you think? Have you heard of the gods of the Thirty-three?" 

​General: "Yes, sir, I have heard of them. And King Pasenadi of Kosala has heard of them too."
Ven Ananda: "General, what do you think? Can King Pasenadi of Kosala topple the gods of the Thirty-three or banish them from that place?"
General: "Sir, King Pasenadi of Kosala cannot even see the gods of the Thirty-three, so how could he topple them or banish them from that place?"
Ven Ananda: "So too, general, those gods who are still subject to affliction and who come back to this human state cannot even see those gods who are no longer subject to affliction and who do not come back to this human state; so how could they topple them or banish them from that place?"

Then King Pasenadi of Kosala asked the Blessed One: "Venerable sir, what is this bhikkhu's name?"
Buddha: "His name is Ananda, great king."
King: "Ananda] he is indeed, venerable sir, and Ananda he appears. What the venerable Ananda has said appears reasonable, what he has said appears to be supported by reason. But, venerable sir, how is it: are there Brahmas?"

Buddha: "Why do you ask that, great king?"
King: "Venerable sir, I was asking whether those Brahmas come back to this human state or whether they do not." Buddha: "Great king, any Brahma who is still subject to affliction comes back to this human state, any Brahma who is no longer subject to affliction does not come back to this [human] state."
Then a man announced to King Pasenadi of Kosala: "Great king, Sanjaya, the brahmin of the Akasa clan, has come."

King Pasenadi of Kosala asked Sanjaya, the brahmin of the Akasa clan: "Brahmin, who introduced this story to the palace?"
Brahmin Sanjaya: "Sire, it was General Vidudabha."
General Vidudabha said: "Sire, it was Sanjaya, the brahmin of the Akasa clan."
Then a man announced to King Pasenadi of Kosala: "Sire, it is time to depart."
King Pasenadi of Kosala said to the Blessed One: "Venerable sir, we have asked the Blessed One about omniscience, and the Blessed One has answered about omniscience; we approve of and accept that answer, and so we are satisfied. We have asked the Blessed One about purification in the four castes, and the Blessed One has answered about purification in the four castes; we approve of and accept that answer, and so we are satisfied. We have asked the Blessed One about the gods, and the Blessed One has answered about the gods; we approve of and accept that answer, and so we are satisfied. We have asked the Blessed One about the Brahmas, and the Blessed One has answered about the Brahmas; we approve of and accept that answer, and so we are satisfied. Whatever we asked the Blessed One, that the Blessed One has answered; we approve of and accept those answers, and so we are satisfied. And now, venerable sir, we depart. We are busy and have much to do."

Buddha: "Now is the time, great king, to do as you think fit."
Then King Pasenadi of Kosala, having delighted and rejoiced in the Blessed One's words, rose from his seat, and after paying homage to the Blessed One, keeping him on his right, he departed. ​

 In this discourse, ​King Pasenadi questions the Buddha about omniscience, the difference between the casts, and about the existence and destinies of the gods and Brahma on whether they return to human realms.

With regards to the question on omniscience, buddha replied : "I recall having actually made the utterance in this way, great king: 'There is no recluse or brahmin who knows all, who sees all, simultaneously; that is not possible.'"
With regards to the question on casts, Buddha said: "There are these four castes, great king: the nobles, the brahmins, the merchants, and the workers. Now if they possessed these five factors of striving(faith, free from illness and affliction, honest and sincere,energetic and wise), it would lead to their welfare and happiness for a long time." 

​With regards to the question on the destiny of the gods, Buddha replied: "Great king, those gods who are still subject to affliction come back to this human state, those gods who are no longer subject to affliction do not come back to this human state." 
​With regards to the question on the destiny of Brahma, Buddha replied: "Great king, any Brahma who is still subject to affliction comes back to this human state, any Brahma who is no longer subject to affliction does not come back to this human state."

At the end of the discourse, brahmin Sañjaya ākāsagotta was charged with having spread a wrong interpretation of the Buddha's teaching but he pushed the blame on Vidūdabha. The arrival of the king's chariot puts an end to the dispute and the king departed with his entourage after thanking buddha for his teachings. 

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