One day, the Buddha was staying at the Deer Park Monastery in the eastern part of Shravasti. In the evening, he stopped his meditation and went outside to sit down. At that time, King Prasenajit of Kosala came to visit him and paid his respects before sitting down beside him.

Seven ascetics with long hair, seven Niganthas (Jain monks), seven naked ascetics, seven who wore only one garment for their practice, and seven wanderers from other sects passed by carrying their necessary belongings for their practices. Their armpit hair, body hair and nails were all very long as they had not trimmed or bathed themselves for a long time.

King Prasenajit stood up from his seat and arranged his upper garment on one shoulder while kneeling on his right leg towards these practitioners passing by the Buddha's dwelling place. He respectfully greeted them three times saying "Venerables! I am King Prasenajit of Kosala." 

After these practitioners left, King Prasenajit asked the Buddha: "World Honored One, are those practitioners who just passed by here Arhats? Are they people who have already attained enlightenment?"

The Buddha replied: "Great king! For someone like you who enjoys various sensual pleasures at home with many children; using different kinds of incense; wearing flower garlands; applying various fragrances and ointments; possessing countless gold and silver - how can you distinguish between an Arhat or an enlightened practitioner? It is difficult to discern or understand."

"Great king! To live together with these practitioners so as to experience their practices requires a long period of time. Even after living together with them for a short period it is still impossible to know whether they observe precepts or not; whether they frequently generate mindfulness or not; whether they are wise or foolish."

"Great king! Similarly, to know whether their practices are pure or impure requires a long period of time living together with them. It is impossible to discern this in a short period of time."

"Great king! Only during disasters and calamities can one's courage, strength and perseverance be demonstrated. Moreover, it takes a long observation period to truly understand someone's character. It is impossible to see through someone in a short amount of time."

"Great king! Similarly, only by frequently conversing and communicating with someone can we possibly know if they possess true wisdom from their daily behavior and speech. A long period of conversation, communication and contact is required; it is still impossible to know if they truly have wisdom in just a short amount of time."

King Pasenadi said, "World Honored One, you are right. Many things cannot be judged by appearances alone. It takes a long time to observe and interact with these practitioners, preferably practicing alongside them and observing them for an extended period of time to determine if they are truly Arhats or not.

Pointing at his guards who were standing far away protecting him, King Pasenadi said to the Buddha, "Many of these guards are well-trained spies with excellent martial arts skills. They are good at reconnaissance and collecting intelligence from various countries. I will send them secretly to investigate and observe the true practice of these practitioners - whether they uphold precepts for a long time, what their daily behavior and speech is like, whether their practice is pure or not. If these practitioners go somewhere where no one knows them, wash off the dirt on their bodies and put on clean clothes after bathing. Then apply various spices and ointments on themselves while tidying up their hair before enjoying all kinds of wonderful food and indulging in sensual pleasures; they have already been bound by their own desires. Their previous behavior as dirty-looking fake practitioners was nothing but shameless deception that cheated believers out of offerings. After investigating and observing them thoroughly, I will decide whether to arrest them for fraud."

The Buddha replied: "Your Majesty, it's not easy to judge whether someone is a genuine practitioner based solely on external appearance such as dress style or behavior or speech in a short period of time; it's difficult indeed! We can't trust someone just because he looks like a practitioner from his outward appearance.

Because many people in this world pretend to be great saints or virtuous people through dressing up like one externally but may not hold any precepts nor possess any wisdom inside which makes him unrestrainedly indulge himself without any restraint whatsoever causing harm everywhere he goes instead! Therefore we need more observation over an extended period regarding how they behave and speak, whether they uphold precepts for a long time, and whether their practice is pure or not. We should use their behavior and speech during long-term pure practice as the basis to distinguish genuine practitioners from fake ones instead of just looking at their dress style or short-term performance of pure practice. It's like an earring made of false material with dirt inside; it looks beautiful on the surface but has no real substance inside. Similarly, brass plated with gold outside is also fake gold. These fake earrings and fake gold may look shiny on the surface but are useless because there is nothing substantial inside.

Similarly, Your Majesty, some people in this world pretend to be great saints or virtuous people by imitating external appearance such as dress style or behavior or speech in a short period of time while pretending to hold precepts and do pure practices only to cheat believers out of offerings! However when they go somewhere where nobody knows them, they will indulge themselves recklessly using fraudulent money obtained from cheating others! They are addicted to desire and lost in greed! These people may look shiny on the surface like practitioners but actually have no real substance inside - hollow decorations like earrings mixed with dirt within them; brass plated with gold outside that is not true gold - worthless seeds that can never grow into anything good! They deceive everywhere they go through dressing up externally while having dirty hearts full of bad qualities pretending to be morally upright practitioners who do pure practices without any impurities whatsoever!

They will eventually be discovered by everyone, despised by all, punished accordingly before falling into one of three evil realms: hell realm (endless suffering), hungry ghost realm (insatiable hunger), animal realm (ignorance). Their endless afflictions and sufferings cannot be described!"

At this point, the Buddha recited a verse:

"The appearance of a person is not easily known,

Do not believe it at first sight;

Those who are skilled can discern its true nature.

It is not for controlling others,

But for the common practice in this world.

Like an earring made of clay,

Or copper plated with gold worth only half a coin,

Everyone adorns themselves with beauty on the outside

While impurities reside within."

Pali original scripture

2. Dutiyavaggo

SN.3.11/(1). Sattajaṭilasuttaṃ

　　 122. Ekaṃ samayaṃ bhagavā sāvatthiyaṃ viharati pubbārāme migāramātupāsāde. Tena kho pana samayena bhagavā sāyanhasamayaṃ paṭisallānā vuṭṭhito bahidvārakoṭṭhake nisinno hoti. Atha kho rājā pasenadi kosalo yena bhagavā tenupasaṅkami; upasaṅkamitvā bhagavantaṃ abhivādetvā ekamantaṃ nisīdi.

　　 Tena kho pana samayena satta ca jaṭilā satta ca nigaṇṭhā satta ca acelakā satta ca ekasāṭakā satta ca paribbājakā parūḷhakacchanakhalomā khārivividhamādāya bhagavato avidūre atikkamanti. Atha kho rājā pasenadi kosalo uṭṭhāyāsanā ekaṃsaṃ uttarāsaṅgaṃ karitvā dakkhiṇajāṇumaṇḍalaṃ pathaviyaṃ nihantvā yena te satta ca jaṭilā satta ca nigaṇṭhā satta ca acelakā satta ca ekasāṭakā satta ca paribbājakā tenañjaliṃ paṇāmetvā tikkhattuṃ nāmaṃ sāvesi– “rājāhaṃ, bhante, pasenadi kosalo …pe… rājāhaṃ, bhante, pasenadi kosalo”ti.

　　 Atha kho rājā pasenadi kosalo acirapakkantesu tesu sattasu ca jaṭilesu sattasu ca nigaṇṭhesu sattasu ca acelakesu sattasu ca ekasāṭakesu sattasu ca paribbājakesu yena bhagavā tenupasaṅkami; upasaṅkamitvā bhagavantaṃ abhivādetvā ekamantaṃ nisīdi. Ekamantaṃ nisinno kho rājā pasenadi kosalo bhagavantaṃ etadavoca– “ye te, bhante, loke arahanto vā arahattamaggaṃ vā samāpannā ete tesaṃ aññatarā”ti.

　　 “Dujjānaṃ kho etaṃ, mahārāja, tayā gihinā kāmabhoginā puttasambādhasayanaṃ ajjhāvasantena kāsikacandanaṃ paccanubhontena mālāgandhavilepanaṃ dhārayantena jātarūparajataṃ sādiyantena– ‘ime vā arahanto, ime vā arahattamaggaṃ samāpannā’”ti.

　　 “Saṃvāsena kho, mahārāja, sīlaṃ veditabbaṃ. Tañca kho dīghena addhunā, na ittaraṃ; manasikarotā, no amanasikarotā; paññavatā, no duppaññena. Saṃvohārena kho, mahārāja, soceyyaṃ veditabbaṃ. Tañca kho dīghena addhunā, na ittaraṃ; manasikarotā, no amanasikarotā; paññavatā, no duppaññena. Āpadāsu kho, mahārāja, thāmo veditabbo. So ca kho dīghena addhunā, na ittaraṃ; manasikarotā, no amanasikarotā; paññavatā, no duppaññena. Sākacchāya kho, mahārāja, paññā veditabbā. Sā ca kho dīghena addhunā, na ittaraṃ; manasikarotā, no amanasikarotā; paññavatā, no duppaññenā”ti.

　　 “Acchariyaṃ bhante, abbhutaṃ bhante! Yāva subhāsitamidaṃ, bhante, bhagavatā– ‘dujjānaṃ kho etaṃ, mahārāja, tayā gihinā kāmabhoginā puttasambādhasayanaṃ ajjhāvasantena kāsikacandanaṃ paccanubhontena mālāgandhavilepanaṃ dhārayantena jātarūparajataṃ sādiyantena – ime vā arahanto, ime vā arahattamaggaṃ samāpannā’ti. Saṃvāsena kho, mahārāja, sīlaṃ veditabbaṃ. Tañca kho dīghena addhunā, na ittaraṃ; manasikarotā, no amanasikarotā; paññavatā, no duppaññena. Saṃvohārena kho mahārāja soceyyaṃ veditabbaṃ. Tañca kho dīghena addhunā, na ittaraṃ; manasikarotā, no amanasikarotā; paññavatā, no duppaññena. Āpadāsu kho, mahārāja, thāmo veditabbo. So ca kho dīghena addhunā, na ittaraṃ; manasikarotā, no amanasikarotā; paññavatā, no duppaññena. Sākacchāya kho, mahārāja, paññā veditabbā. Sā ca kho dīghena addhunā, na ittaraṃ; manasikarotā, no amanasikarotā; paññavatā, no duppaññenā”ti.

　　 “Ete, bhante, mama purisā carā ocarakā janapadaṃ ocaritvā āgacchanti. Tehi paṭhamaṃ ociṇṇaṃ ahaṃ pacchā osāpayissāmi. Idāni te, bhante, taṃ rajojallaṃ pavāhetvā sunhātā suvilittā kappitakesamassū odātavatthā pañcahi kāmaguṇehi samappitā samaṅgībhūtā paricāressantī”ti.

　　 Atha kho bhagavā etamatthaṃ viditvā tāyaṃ velāyaṃ imā gāthāyo abhāsi–

　　 “Na vaṇṇarūpena naro sujāno, na vissase ittaradassanena.

　　 Susaññatānañhi viyañjanena, asaññatā lokamimaṃ caranti.

　　 “Patirūpako mattikākuṇḍalova, lohaḍḍhamāsova suvaṇṇachanno.

　　 Caranti loke parivārachannā, anto asuddhā bahi sobhamānā”ti.