Thus have I heard. On one occasion the Blessed One was dwelling at Savatthi in Jeta's Grove, Anathapindika's Park. There the Blessed One said this: "Bhikkhus, just as all the rafters of a peaked house lead to the roof peak and converge upon the root peak, and all are removed when the roof peak is removed, so too all unwholesome states are rooted in ignorance and converge upon ignorance, and all are uprooted when ignorance is uprooted. Therefore, bhikkhus, you should train yourselves thus: 'We will dwell diligently.' Thus should you train yourselves."
(As rafters depend on the roof-peak, unwholesome qualities depend on ignorance.)
SN 20.2 Nakhasikha Sutta: The Fingernail
At Savatthi. Then the Blessed One took up a little bit of soil in his fingernail and addressed the bhikkhus thus: "Bhikkhus, what do you think, which is more: the little bit of soil that I have taken-up in my fingernail or the great earth?" "Venerable sir, the great earth is more. The little bit of soil that the Blessed One has taken up in his fingernail is trifling. Compared to the great earth, it is not calculable, does not bear comparison, does not amount even to a fraction." "So too, bhikkhus, those beings who are reborn among human beings are few. But those beings are more numerous who are reborn elsewhere than among human beings. Therefore, bhikkhus, you should train yourselves thus: 'We will dwell diligently.' Thus should you train yourselves."
(As the dirt in a fingernail is smaller than the great earth, the beings reborn as humans are few.)
SN 20.3 Kula Sutta: Families
At Savatthi."Bhikkhus, just as it is easy for burglars to assail those families that have many women and few men, so too it is easy for non-human beings to assail a bhikkhu who has not developed and cultivated the liberation of mind by loving kindness."
"Just as it is difficult for burglars to assail those families that have few women and many men, so too it is difficult for nonhuman beings to assail a bhikkhu who has developed and cultivated the liberation of mind by loving kindness. Therefore, bhikkhus, you should train yourselves thus: 'We will develop and cultivate the liberation of mind by loving kindness, make it our vehicle, make it our basis, stabilize it, exercise ourselves in it, and fully perfect it.' Thus should you train yourselves."
(As a family with few men and many women is easily attacked, non-human beings may attack a mendicant without loving kindness. )
SN 20.4 Okkhā Sutta: Pots of Food
At Savatthi. "Bhikkhus, if someone were to give away a hundred pots of food as charity in the morning, a hundred pots of food as charity at noon, and a hundred pots of food as charity in the evening, and if someone else were to develop a mind of loving kindness even for the time it takes to pull a cow's udder, either in the morning, at noon, or in the evening, this would be more fruitful than the former."
"Therefore, bhikkhus, you should train yourselves thus: 'We will develop and cultivate the liberation of mind by loving kindness, make it our vehicle, make it our basis, stabilize it, exercise ourselves in it, and fully perfect it.' Thus should you train yourselves."
(Loving kindness is more beneficial than generosity.)
SN 20.5 Satti Sutta: The Spear
At Savatthi. "Bhikkhus, suppose there was a sharp-pointed spear, and a man would come along thinking: 'I will bend back this sharp-pointed spear with my hand or fist, twist it out of shape, and twirl it around.' What do you think bhikkhus, would it be possible for that man to do so?" "No, venerable sir. For what reason? Because it is not easy to bend back that sharp-pointed spear with one's hand or fist, to twist it out of shape, or to twirl it around. That man would only experience fatigue and vexation. "
"So too, bhikkhus, when a bhikkhu has developed and cultivated the liberation of mind by loving kindness, made it a vehicle, made it a basis, stabilized it, exercised himself in it, and fully perfected it, if a non-human being thinks he can overthrow his mind, that nonhuman being would only experience fatigue and vexation. "
"Therefore, bhikkhus, you should train yourselves thus: 'We will develop and cultivate the liberation of mind by loving kindness, make it our vehicle, make it our basis, stabilize it, exercise ourselves in it, and fully perfect it.' Thus should you train yourselves."
(As it is not possible to bend back a spear, it is not possible to overthrow a monk who has developed loving kindness.)
SN 20.6 Dhanuggaha Sutta : The Archers
At Savatthi. "Bhikkhus, suppose there were four firm-bowed archers, trained, dexterous, experienced, standing in each of the four directions. Then a man would come along, thinking: 'I will catch the arrows shot by these four archers in each of the four directions before they reach the ground and then I will bring them back.' What do you think, bhikkhus, would this be enough to say: 'That man is a speedster endowed with supreme speed'?"
"Venerable sir, even if he could catch the arrow shot by one archer before it reached the ground and could bring it back, that would be enough to say: 'That man is a speedster endowed with supreme speed.' There is no need to speak about the arrows shot by all four archers!"
"Bhikkhus, as swift as that man is, still swifter are the sun and moon. As swift as that man is, and as swift as are the sun and moon, and as swift as are the deities that run before the sun and moon, the vital formations perish even more swiftly than that. Therefore, bhikkhus, you should train yourselves thus: 'We will dwell diligently.' Thus should you train yourselves."
(Only a speedster could catch arrows in flight, yet conditioned phenomena perish faster than that.)
SN 20.7 Āṇi Sutta: The Drum Peg
At Savatthi. "Bhikkhus, once in the past the Dasarahas had a kettle drum called the Summoner. When the Summoner became cracked, the Dasarahas inserted another peg. Eventually the time came when the Summoner's original drum head had disappeared and only a collection of pegs remained. "
"So too, bhikkhus, the same thing will happen with the bhikkhus in the future. When those discourses spoken by the Tathagata that are deep, deep in meaning, supra-mundane, dealing with emptiness, are being recited, they will not be eager to listen to them, nor lend an ear to them, nor apply their minds to understand them; and they will not think those teachings should be studied and mastered. But when those discourses that are mere poetry composed by poets, beautiful in words and phrases, created by outsiders, spoken by their disciples, are being recited, they will be eager to listen to them, will lend an ear to them, will apply their minds to understand them; and they will think those teachings should be studied and mastered. In this way, bhikkhus, those discourses spoken by the Tathagata that are deep, deep in meaning, supra-mundane, dealing with emptiness, will disappear. "
"Therefore, bhikkhus, you should train yourselves thus: 'When those discourses spoken by the Tathagata that are deep, deep in meaning, supra-mundane, dealing with emptiness, are being recited, we will be eager to listen to them, will lend an ear to them, will apply our minds to understand them; and we will think those teachings should be studied and mastered.' Thus should you train yourselves." (As an ancient drum has disintegrated, so too will the true teachings disappear.) SN 20.8 Kaliṅgara Sutta: Blocks of Wood
Thus have I heard. On one occasion the Blessed One was dwelling at Vesali in the Great Wood in the Hall with the Peaked Roof. There the Blessed One addressed the bhikkhus thus: "Bhikkhus!" "Venerable sir!" those bhikkhus replied.
The Blessed One said this: "Bhikkhus, now the Licchavis dwell using blocks of wood as cushions; they are diligent and ardent in exercise. King Ajatasattu of Magadha, the Videhan son, does not gain access to them; he does not get a hold on them. But in the future the Licchavis will become delicate, with soft and tender hands and feet; they will sleep until sunrise on soft beds with pillows of cotton wool. Then King Ajatasattu of Magadha will gain access to them; then he will get a hold on them. "
"Bhikkhus, now the bhikkhus dwell using blocks of wood as cushions; they are diligent and ardent in striving. Mara the Evil One does not gain access to them; he does not get a hold on them. But in the future the bhikkhus will become delicate, with soft and tender hands and feet; they will sleep until sunrise on soft beds with pillows of cotton wool. Then Mara the Evil One will gain access to them; he will get a hold on them. "
"Therefore, bhikkhus, you should train yourselves thus: 'Using blocks of wood as cushions, we will dwell diligent and ardent in striving: Thus should you train yourselves."
(Warriors who sleep on wooden pillows remain vigilant, and so it is for the spiritual seeker.)
SN 20.9 Nāga Sutta: The Bull Elephant
Thus have I heard. On one occasion the Blessed One was dwelling at Savatthi in Jeta's Grove, Anathapindika's Park. Now on that occasion a certain newly ordained bhikkhu was approaching families excessively. The other bhikkhus told him: "The venerable one should not approach families excessively," but when he was being admonished by them he said: "These elder bhikkhus think they can approach families, so why can't I?"
Then a number of bhikkhus approached the Blessed One, paid homage to him, sat down to one side, and reported this matter to the Blessed One. The Blessed One said: "Bhikkhus, once in the past there was a great lake in a forest, with bull elephants dwelling in its vicinity. Those elephants would plunge into the lake, pull up lotus stalks with their trunks, and, having washed them thoroughly, would chew them and swallow them free from mud. This increased their beauty and strength, and on that account they did not meet death or deadly suffering. "
"Their young offspring, emulating those great bull elephants, would plunge into the lake and pull up lotus stalks with their trunks, but without washing them thoroughly, without chewing them, they would swallow them along with the mud. This did not increase their beauty and strength, and on that account they met death or deadly suffering. "
"So too, bhikkhus, here the elder bhikkhus dress in the morning and, taking bowl and robe, enter a village or town for alms. There they speak on the Dhamma, and the laypeople show their confidence to them. They use their gains without being tied to them, un-infatuated with them, not blindly absorbed in them, seeing the danger in them and understanding the escape. This increases their beauty and strength, and on that account they do not meet death or deadly suffering. "
"The newly ordained bhikkhus, emulating the elder bhikkhus, dress in the morning and, taking bowl and robe, enter a village or town for alms. There they speak on the Dhamma, and the laypeople show their confidence to them. They use their gains while being tied to them, infatuated with them, blindly absorbed in them, not seeing the danger in them and not understanding the escape. This does not increase their beauty and strength, and on that account they meet death or deadly suffering."
"Therefore, bhikkhus, you should train yourselves thus: 'We will use our gains without being tied to them, un-infatuated with them, not blindly absorbed in them, seeing the danger in them and understanding the escape: Thus should you train yourselves."
(A monk who overly associates with the laity is like an elephant calf who tries to copy the great bull elephants.)
SN 20.10 Biḷāra Sutta: The Cat At Savatthi. Now on that occasion a certain bhikkhu was socializing with families excessively. The other bhikkhus told him: "The venerable one should not socialize with families excessively," but though he was admonished by them he did not desist. Then a number of bhikkhus approached the Blessed One, paid homage to him, sat down to one side, and reported this matter to the Blessed One.
The Blessed One said:"Bhikkhus, once in the past a cat stood by an alley or a drain or a rubbish bin watching for a little mouse, thinking: 'When this little mouse comes out for food, right there I will grab it and eat it.' Then that mouse came out for food, and the cat grabbed it and swallowed it hastily, without chewing it. Then that little mouse ate the cat's intestines and mesentery, and on that account the cat met with death and deadly suffering. "
"So too, bhikkhus, here some bhikkhu dresses in the morning and, taking bowl and robe, enters a village or town for alms with body, speech, and mind unguarded, without setting up mindfulness, unrestrained in his sense faculties. He sees women there lightly clad or lightly attired and lust invades his mind. With his mind invaded by lust he meets death or deadly suffering. For this, bhikkhus, is death in the Noble One's Discipline: that one gives up the training and returns to the lower life. This is deadly suffering: that one commits a certain defiled offence of a kind that allows for rehabilitation."
"Therefore, bhikkhus, you should train yourselves thus: 'We will enter a village or town for alms with body, speech, and mind guarded, with mindfulness set up, restrained in our sense faculties.' Thus should you train yourselves."
(As a cat may suffer from eating too hastily, so a monk may suffer by not restraining senses.)
SN 20.11 Siṅgāla Sutta: The Jackal (1)
At Savatthi. "Bhikkhus, did you hear an old jackal howling at the flush of dawn?" "Yes, venerable sir." "That old jackal is afflicted with a disease called mange. Yet he still goes wherever he wants, stands wherever he wants, sits wherever he wants, lies down wherever he wants, and a cool breeze even blows upon him. It would be good for a certain person here claiming to be a follower of the Sakyan son if he were to experience even such a form of individual existence."
"Therefore, bhikkhus, you should train yourselves thus: 'We will dwell diligently.' Thus should you train yourselves."
(A mangy jackal howls in discomfort, but even that would be a good rebirth for some.)
SN 20.12 Dutiyasiṅgāla Sutta: The Jackal (2)
At Savatthi. "Bhikkhus, did you hear an old jackal howling at the flush of dawn?" "Yes, venerable sir." "There may be some gratitude and thankfulness in that old jackal, but there is no gratitude and thankfulness in a certain person here claiming to be a follower of the Sakyan son."
"Therefore, bhikkhus, you should train yourselves thus: 'We will be grateful and thankful, and we will not overlook even the least favour done to us.' Thus should you train yourselves." (An old jackal howls at dawn, but even they have more gratitude than some)
References: 1. www.accesstoinsight.org 2. https://suttacentral.net/ 3. The middle length discourses of the Buddha (Bhikkhu Bodhi)