The Buddha uses a simile of a cat and a mouse to illustrate how not setting up mindfulness and being unrestrained in the sense faculties can lead to death or deadly suffering.
Sāvatthiyaṁ viharati.
At Sāvatthi.
Tena kho pana samayena aññataro bhikkhu ativelaṁ kulesu cārittaṁ āpajjati.
At that time, a certain bhikkhu was engaging with families excessively.
Tamenaṁ bhikkhū evamāhaṁsu: “māyasmā ativelaṁ kulesu cārittaṁ āpajjī”ti.
The other bhikkhus said to him: “Venerable, do not engage with families excessively.”
So bhikkhu bhikkhūhi vuccamāno na viramati.
But even when spoken to by the other bhikkhus, he did not desist from this.
Atha kho sambahulā bhikkhū yena bhagavā tenupasaṅkamiṁsu; upasaṅkamitvā bhagavantaṁ abhivādetvā ekamantaṁ nisīdiṁsu. Ekamantaṁ nisinnā kho te bhikkhū bhagavantaṁ etadavocuṁ: “idha, bhante, aññataro bhikkhu ativelaṁ kulesu cārittaṁ āpajjati. Tamenaṁ bhikkhū evamāhaṁsu: ‘māyasmā ativelaṁ kulesu cārittaṁ āpajjī’ti. So bhikkhu bhikkhūhi vuccamāno na viramatī”ti.
Then several bhikkhus went to the Blessed One. After approaching and paying homage to him, they sat down to one side. Once seated, those bhikkhus said to the Blessed One: “Here, venerable sir, a certain bhikkhu is engaging with families excessively. The bhikkhus said this to him: ‘Venerable, do not engage with families excessively.’ But even when spoken to by the other bhikkhus, he does not desist from this.”
“Bhūtapubbaṁ, bhikkhave, biḷāro sandhisamalasaṅkaṭīre ṭhito ahosi mudumūsiṁ maggayamāno: ‘yadāyaṁ mudumūsi gocarāya pakkamissati, tattheva naṁ gahetvā khādissāmī’ti. Atha kho so, bhikkhave, mudumūsi gocarāya pakkāmi. Tamenaṁ biḷāro gahetvā sahasā saṅkhāditvā ajjhohari. Tassa so mudumūsi antampi khādi, antaguṇampi khādi. So tatonidānaṁ maraṇampi nigacchi maraṇamattampi dukkhaṁ.
“Bhikkhus, once in the past a cat stood near a rubbish heap at a crossroads, watching for a young mouse, thinking: ‘When this young 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 young mouse ate the cat’s intestines and |mesentery::intestine string [antaguṇa]|, and on that account the cat met with death or deadly suffering.
Evameva kho, bhikkhave, idhekacco bhikkhu pubbaṇhasamayaṁ nivāsetvā pattacīvaramādāya gāmaṁ vā nigamaṁ vā piṇḍāya pavisati arakkhiteneva kāyena arakkhitāya vācāya arakkhitena cittena, anupaṭṭhitāya satiyā, asaṁvutehi indriyehi. So tattha passati mātugāmaṁ dunnivatthaṁ vā duppārutaṁ vā. Tassa mātugāmaṁ disvā dunnivatthaṁ vā duppārutaṁ vā rāgo cittaṁ anuddhaṁseti. So rāgānuddhaṁsena cittena maraṇaṁ vā nigacchati maraṇamattaṁ vā dukkhaṁ.
So too, bhikkhus, here some bhikkhu dresses early in the morning and, taking alms bowl and outer robe, enters a village or town for alms with body |unguarded::unprotected [arakkhita]|, speech unguarded, and mind unguarded, without setting up |mindfulness::recollection of the body, feelings, mind, and mental qualities, observing them clearly with sustained attention, free from craving and distress [sati]|, |unrestrained::uncontrolled [asaṃvuta]| in his sense faculties. There he sees a woman who is scantily clothed or improperly covered. On seeing the woman who is scantily clothed or improperly covered, |lust::passion, infatuation, desire [rāga]| invades his mind. With his mind invaded by lust, he meets death or deadly suffering.
Maraṇañhetaṁ, bhikkhave, ariyassa vinaye yo sikkhaṁ paccakkhāya hīnāyāvattati. Maraṇamattañhetaṁ, bhikkhave, dukkhaṁ yadidaṁ aññataraṁ saṅkiliṭṭhaṁ āpattiṁ āpajjati. Yathārūpāya āpattiyā vuṭṭhānaṁ paññāyati.
For this, bhikkhus, is death in the Noble One’s |Vinaya::code of monastic discipline rules, training [vinaya]|: that one gives up the training and |reverts back to the household life::returns to lay-life, secular world [hīnāyāvattati]|. This is deadly suffering: that one commits a certain |defiled::tainted, corrupted [saṅkiliṭṭha]| offense of a kind that allows for rehabilitation.
Tasmātiha, bhikkhave, evaṁ sikkhitabbaṁ: ‘rakkhiteneva kāyena rakkhitāya vācāya rakkhitena cittena, upaṭṭhitāya satiyā, saṁvutehi indriyehi gāmaṁ vā nigamaṁ vā piṇḍāya pavisissāmā’ti. Evañhi vo, bhikkhave, sikkhitabban”ti.
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, bhikkhus, you should train yourselves.”
At Sāvatthi.
At that time, a certain bhikkhu was engaging with families excessively.
The other bhikkhus said to him: “Venerable, do not engage with families excessively.”
But even when spoken to by the other bhikkhus, he did not desist from this.
Then several bhikkhus went to the Blessed One. After approaching and paying homage to him, they sat down to one side. Once seated, those bhikkhus said to the Blessed One: “Here, venerable sir, a certain bhikkhu is engaging with families excessively. The bhikkhus said this to him: ‘Venerable, do not engage with families excessively.’ But even when spoken to by the other bhikkhus, he does not desist from this.”
“Bhikkhus, once in the past a cat stood near a rubbish heap at a crossroads, watching for a young mouse, thinking: ‘When this young 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 young mouse ate the cat’s intestines and |mesentery::intestine string [antaguṇa]|, and on that account the cat met with death or deadly suffering.
So too, bhikkhus, here some bhikkhu dresses early in the morning and, taking alms bowl and outer robe, enters a village or town for alms with body |unguarded::unprotected [arakkhita]|, speech unguarded, and mind unguarded, without setting up |mindfulness::recollection of the body, feelings, mind, and mental qualities, observing them clearly with sustained attention, free from craving and distress [sati]|, |unrestrained::uncontrolled [asaṃvuta]| in his sense faculties. There he sees a woman who is scantily clothed or improperly covered. On seeing the woman who is scantily clothed or improperly covered, |lust::passion, infatuation, desire [rāga]| 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 |Vinaya::code of monastic discipline rules, training [vinaya]|: that one gives up the training and |reverts back to the household life::returns to lay-life, secular world [hīnāyāvattati]|. This is deadly suffering: that one commits a certain |defiled::tainted, corrupted [saṅkiliṭṭha]| offense 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, bhikkhus, you should train yourselves.”
Sāvatthiyaṁ viharati.
Tena kho pana samayena aññataro bhikkhu ativelaṁ kulesu cārittaṁ āpajjati.
Tamenaṁ bhikkhū evamāhaṁsu: “māyasmā ativelaṁ kulesu cārittaṁ āpajjī”ti.
So bhikkhu bhikkhūhi vuccamāno na viramati.
Atha kho sambahulā bhikkhū yena bhagavā tenupasaṅkamiṁsu; upasaṅkamitvā bhagavantaṁ abhivādetvā ekamantaṁ nisīdiṁsu. Ekamantaṁ nisinnā kho te bhikkhū bhagavantaṁ etadavocuṁ: “idha, bhante, aññataro bhikkhu ativelaṁ kulesu cārittaṁ āpajjati. Tamenaṁ bhikkhū evamāhaṁsu: ‘māyasmā ativelaṁ kulesu cārittaṁ āpajjī’ti. So bhikkhu bhikkhūhi vuccamāno na viramatī”ti.
“Bhūtapubbaṁ, bhikkhave, biḷāro sandhisamalasaṅkaṭīre ṭhito ahosi mudumūsiṁ maggayamāno: ‘yadāyaṁ mudumūsi gocarāya pakkamissati, tattheva naṁ gahetvā khādissāmī’ti. Atha kho so, bhikkhave, mudumūsi gocarāya pakkāmi. Tamenaṁ biḷāro gahetvā sahasā saṅkhāditvā ajjhohari. Tassa so mudumūsi antampi khādi, antaguṇampi khādi. So tatonidānaṁ maraṇampi nigacchi maraṇamattampi dukkhaṁ.
Evameva kho, bhikkhave, idhekacco bhikkhu pubbaṇhasamayaṁ nivāsetvā pattacīvaramādāya gāmaṁ vā nigamaṁ vā piṇḍāya pavisati arakkhiteneva kāyena arakkhitāya vācāya arakkhitena cittena, anupaṭṭhitāya satiyā, asaṁvutehi indriyehi. So tattha passati mātugāmaṁ dunnivatthaṁ vā duppārutaṁ vā. Tassa mātugāmaṁ disvā dunnivatthaṁ vā duppārutaṁ vā rāgo cittaṁ anuddhaṁseti. So rāgānuddhaṁsena cittena maraṇaṁ vā nigacchati maraṇamattaṁ vā dukkhaṁ.
Maraṇañhetaṁ, bhikkhave, ariyassa vinaye yo sikkhaṁ paccakkhāya hīnāyāvattati. Maraṇamattañhetaṁ, bhikkhave, dukkhaṁ yadidaṁ aññataraṁ saṅkiliṭṭhaṁ āpattiṁ āpajjati. Yathārūpāya āpattiyā vuṭṭhānaṁ paññāyati.
Tasmātiha, bhikkhave, evaṁ sikkhitabbaṁ: ‘rakkhiteneva kāyena rakkhitāya vācāya rakkhitena cittena, upaṭṭhitāya satiyā, saṁvutehi indriyehi gāmaṁ vā nigamaṁ vā piṇḍāya pavisissāmā’ti. Evañhi vo, bhikkhave, sikkhitabban”ti.