​MN 122 Mahasunnata Sutta: The Greater Discourse on Voidness 

Thus have i heard. 

On one occasion the Blessed One was living in the Sakyan country at Kapilavatthu in Nigrodha's Park. Then, when it was morning, the Blessed One dressed, and taking his bowl and outer robe, went into Kapilavatthu for alms. After returning from his alms round, he went for his daytime abiding to the dwelling of Kalakhemaka the Sakyan.

Now on that occasion there were many resting places prepared in Kalakhemaka the Sakyan's dwelling. When the Blessed One saw this, he thought: "There are many resting places prepared in Kalakhemaka the Sakyan's dwelling. Do many bhikkhus live there?" Now on that occasion the venerable Ananda, along with many bhikkhus, was busy making robes at Ghata the Sakyan's dwelling.

Then in the evening, the Blessed One rose from retreat and went to Ghata the Sakyan's dwelling. There he sat down on a seat made ready and asked the venerable Ananda: "Ananda, there are many resting places prepared in Kalakhemaka the Sakyan's dwelling. Do many bhikkhus live there?"
Ananda:"Venerable sir, many resting places have been prepared in Kalakhemaka the Sakyan's dwelling. Many bhikkhus are living there. This is our time for making robes, venerable sir."

Buddha: "Ananda, a bhikkhu does not shine by delighting in company, by taking delight in company, by devoting himself to delight in company; by delighting in society, by taking delight in society, by rejoicing in society. Indeed, Ananda, it is not possible that a bhikkhu who delights in company, takes delight in company, and devotes himself to delight in company, who delights in society, takes delight in society, and rejoices in society, will ever obtain at will, without trouble or difficulty, the bliss of renunciation, the bliss of seclusion, the bliss of peace, the bliss of enlightenment. But it can be expected that when a bhikkhu lives alone, withdrawn from society, he will obtain at will, without trouble or difficulty, the bliss of renunciation, the bliss of seclusion, the bliss of peace, the bliss of enlightenment." 
"Indeed, Ananda, it is not possible that a bhikkhu who delights in company, takes delight in company, and devotes himself to delight in company, who delights in society, takes delight in society, and rejoices in society, will ever enter upon and abide in either the deliverance of mind that is temporary and delectable or in the deliverance of mind] that is perpetual and unshakeable. But it can be expected that when a bhikkhu lives alone, withdrawn from society, he will enter upon and abide in the deliverance of mind that is temporary and delectable or in the deliverance of mind that is perpetual and unshakeable."

"I do not see even a single kind of form, Ananda, from the change and alteration of which there would not arise sorrow, lamentation, pain, grief, and despair in one who lusts for it and takes delight in it. However, Ananda, there is this abiding discovered by the Tathagata: to enter and abide in voidness internally by giving no attention to all signs. If, while the Tathagata is abiding thus, he is visited by bhikkhus or bhikkhunis, by men or women lay followers, by kings or kings' ministers, by other sectarians or their disciples, then with a mind leaning to seclusion, tending and inclining to seclusion, withdrawn, delighting in renunciation, and altogether done with things that are the basis for taints, he invariably talks to them in a way concerned with dismissing them."

"Therefore, Ananda, if a bhikkhu should wish: 'May I enter upon and abide in voidness internally,' he should steady his mind internally, quiet it, bring it to singleness, and concentrate it. And how does he steady his mind internally, quiet it, bring it to singleness, and concentrate it? Here, Ananda, quite secluded from sensual pleasures, secluded from unwholesome states, a bhikkhu enters upon and abides in the first jhana... the second jhana...the third jhana...the fourth jhana, which has neither-pain-nor-pleasure and purity of mindfulness due to equanimity. That is how a bhikkhu steadies his mind internally, quiets it, brings it to singleness, and concentrates it."

"Then he gives attention to voidness internally. While he is giving attention to voidness internally, his mind does not enter into voidness internally or acquire confidence, steadiness, and decision. When that is so, he understands thus: 'While I am giving attention to voidness internally, my mind does not enter into voidness internally or acquire confidence, steadiness, and decision.' In this way he has full awareness of that. He gives attention to voidness externally.. .He gives attention to voidness internally and externally...He gives attention to imperturbability. While he is giving attention to imperturbability, his mind does not enter into imperturbability or acquire confidence, steadiness, and decision. When that is so, he understands thus: 'While I am giving attention to imperturbability, my mind does not enter into imperturbability or acquire confidence, steadiness, and decision.' In this way he has full awareness of that."
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"Then that bhikkhu should steady his mind internally, quiet it, bring it to singleness, and concentrate it on that same sign of concentration as before. Then he gives attention to voidness internally. While he is giving attention to voidness internally, his mind enters into voidness internally and acquires confidence, steadiness, and decision. When that is so, he understands thus: 'While I am giving attention to voidness internally, my mind enters into voidness internally and acquires confidence, steadiness, and decision.' In this way he has full awareness of that. "He gives attention to voidness externally...He gives attention to voidness internally and externally...He gives attention to imperturbability. While he is giving attention to imperturbability, his mind enters into imperturbability and acquires confidence, steadiness, and decision. When that is so, he understands thus: 'While I am giving attention to imperturbability, my mind enters into imperturbability and acquires confidence, steadiness, and decision.' In this way he has full awareness of that."

"When a bhikkhu abides thus, if his mind inclines to walking, he walks, thinking: 'While I am walking thus, no evil unwholesome states of covetousness and grief will beset me.'  In this way he has full awareness of that. And when a ​
bhikkhu abides thus, if his mind inclines to standing, he stands...If his mind inclines to sitting, he sits...If his mind inclines to lying down, he lies down, thinking: 'While I am lying down thus, no evil unwholesome states will beset me.' In this way he has full awareness of that. "
"When a bhikkhu abides thus, if his mind inclines to talking, he resolves: 'Such talk as is low, vulgar, coarse, ignoble, un-beneficial, and which does not lead to disenchantment, dispassion, cessation, peace, direct knowledge, enlightenment, and Nibbana, that is talk of trivialities, the origin of the world, ...whether things are so or are not so: such talk I shall not utter.' In this way he has full awareness of that."

"But he resolves: 'Such talk as deals with effacement, as favors the mind's release, and which leads to complete disenchantment, dispassion, cessation, peace, direct knowledge, enlightenment, and Nibbana, that is, talk on wanting little, on contentment, seclusion, aloofness from society, arousing energy, virtue, concentration, wisdom, deliverance, knowledge and vision of deliverance: such talk I shall utter.' In this way he has full awareness of that."

"When a bhikkhu abides thus if his mind inclines to thinking, he resolves: 'Such thoughts as are low, vulgar, coarse, ignoble, un-beneficial, and which do not lead to disenchantment, dispassion, cessation, peace, direct knowledge, enlightenment, and Nibbana, that is, thoughts of sensual desire, thoughts of ill will, and thoughts of cruelty: such thoughts I shall not think.' In this way he has full awareness of that."

"But he resolves: 'Such thoughts as are noble and emancipating, and lead the one who practices in accordance with them to the complete destruction of suffering, that is, thoughts of renunciation, thoughts of non-ill will, and thoughts of non-cruelty: such thoughts I shall think.' In this way he has full awareness of that."
"Ananda, there are these five cords of sensual pleasure. What five? Forms cognizable by the eye that are wished for, desired, agreeable, and like-able, connected with sensual desire and provocative of lust. Sounds cognizable by the ear...Odors cognizable by the nose...Flavors cognizable by the tongue... Tangibles cognizable by the body that are wished for, desired, agreeable, and like-able, connected with sensual desire and provocative of lust. These are the five cords of sensual pleasure."

"Herein a bhikkhu should constantly review his own mind thus: 'Does any mental excitement concerning these five cords of sensual pleasure ever arise in me on any occasion?' If, on reviewing his mind, the bhikkhu understands: 'Mental excitement concerning these five cords of sensual pleasure does arise in me on certain occasions,' then he understands: 'Desire and lust for the five cords of sensual pleasure are un-abandoned in me.' In this way he has full awareness of that. But if, on reviewing his mind, the bhikkhu understands: 'No mental excitement concerning these five cords of sensual pleasure arises in me on any occasion,' then he understands: 'Desire and lust for the five cords of sensual pleasure are abandoned in me.' In this way he has full awareness of that."

"Ananda, there are these five aggregates affected by clinging, in regard to which a bhikkhu should abide contemplating rise and fall thus: 'Such is material form/feeling/perception/formations/consciousness such its arising, such its disappearance.' When he abides contemplating rise and fall in these five aggregates affected by clinging, the conceit 'I am' based on these five aggregates affected by clinging is abandoned in him. When that is so, that bhikkhu understands: 'The conceit "I am" based on these five aggregates affected by clinging is abandoned in me.' In that way he has full awareness of that. "

"These states have an entirely wholesome basis; they are noble, supra-mundane, and inaccessible to the Evil One. What do you think, Ananda? What good does a disciple see that he should seek the Teacher's company even if he is told to go away?"
Ananda: "Venerable sir, our teachings are rooted in the Blessed One, guided by the Blessed One, have the Blessed One as their resort. ​It would be good if the Blessed One would explain the meaning of these words. Having heard it from the Blessed One, the bhikkhus will remember it."
"Ananda, a disciple should not seek the Teacher's company for the sake of discourses, stanzas, and expositions. Why is that? For a long time, Ananda, you have learned the teachings, remembered them, recited them verbally, examined them with the mind, and penetrated them well by view. But such talk as deals with effacement, as favors the mind's release, and which leads to complete disenchantment, dispassion, cessation, peace, direct knowledge, enlightenment, and Nibbana, that is, talk on wanting little, on contentment, seclusion, aloofness from society, arousing energy, virtue, concentration, wisdom, deliverance, knowledge and vision of deliverance: for the sake of such talk a disciple should seek the Teacher's company even if he is told to go away."

"Since this is so, Ananda, a teacher's undoing may come about, a pupil's undoing may come about, and the undoing of one who lives the holy life may come about. And how does a teacher's undoing come about? Here some teacher resorts to a secluded resting place: the forest, the root of a tree, a mountain, a ravine, a hillside cave, a charnel ground, a jungle thicket, an open space, a heap of straw. While he lives thus withdrawn, brahmins and householders from town and country visit him, and as a result he goes astray, becomes filled with desire, succumbs to craving, and reverts to luxury. This teacher is said to be undone by the teacher's undoing. He has been struck down by evil unwholesome states that defile, bring renewal of being, give trouble, ripen in suffering, and lead to future birth, ageing, and death. This is how the teacher's undoing comes about."

"And how does a pupil's undoing come about? A pupil of that teacher, emulating the teacher's seclusion, resorts to a secluded resting place.... While he lives thus withdrawn, brahmins and householders from town and country visit him, and as a result he goes astray, becomes filled with desire, succumbs to craving, and reverts to luxury. This pupil is said to be undone by the pupil's undoing. He has been struck down by evil unwholesome states that defile, bring renewal of being, give trouble, ripen in suffering, and lead to lead to future birth, aging, & death. Such is the student's undoing."
"And how does the undoing of one who lives the holy life come about? Here a Tathagata appears in the world, accomplished and 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. He resorts to a secluded resting place. While he lives thus withdrawn, brahmins and householders from town and country visit him, yet he does not go astray, or become filled with desire, succumb to craving, and revert to luxury.But a disciple of this teacher, emulating his teacher's seclusion, resorts to a secluded resting place. While he lives thus withdrawn, brahmins and householders from town and country visit him, and as a result he goes astray, becomes filled with desire, succumbs to craving, and reverts to luxury. This one who lives the holy life is said to be undone by the undoing of one who lives the holy life. He has been struck down by evil unwholesome states that defile, bring renewal of being, give trouble, ripen in suffering, and lead to future birth, ageing, and death. Thus there comes to be the undoing of one who leads the holy life. And herein, Ananda, the undoing of one who leads the holy life has a more painful result, a more bitter result, than the teacher's undoing or the pupil's undoing, and it even leads to perdition."

"Therefore, Ananda, behave towards me with friendliness, not with hostility. That will lead to your welfare and happiness for a long time. And how do disciples behave towards the Teacher with hostility, not with friendliness? Here, Ananda, compassionate and seeking their welfare, the Teacher teaches the Dhamma to the disciples out of compassion: "This is for your welfare, this is for your happiness.' His disciples do not want to hear or give ear or exert their minds to understand; they err and turn aside from the Teacher's Dispensation. Thus do disciples behave towards the Teacher with hostility, not with friendliness."

"And how do disciples behave towards the Teacher with friendliness, not with hostility? Here, Ananda, compassionate and seeking their welfare, the Teacher teaches the Dhamma to the disciples out of compassion: "This is for your welfare, this is for your happiness.' His disciples want to hear and give ear and exert their minds to understand; they "do not err and turn aside from the Teacher's Dispensation. Thus do disciples behave towards the Teacher with friendliness, not with hostility.  Therefore, Ananda, behave towards me with friendliness, not with hostility. That will lead to your welfare and happiness for a long time."

"I shall not treat you as the potter treats the raw damp clay. Repeatedly restraining you, I shall speak to you, Ananda. Repeatedly admonishing you, I shall speak to you, Ananda. The sound core will stand the test."

That is what the Blessed One said. The venerable Ananda was satisfied and delighted in the Blessed One's words. 
In summary, the Buddha encourages living in solitude and describes the effort the disciple must make to return again and again to each stage of the path when upon evaluation of his accomplishments he realizes he is not yet satisfied that he is completely liberated. He emphasizes the importance of practicing the four foundations of mindfulness. and the need to abandon sensual cravings. 
References: 
1. www.accesstoinsight.org
2. https://suttacentral.net/
3. The middle length discourses of the Buddha (Bhikkhu Bodhi)