Thanasutta 3.4

3.4

‘Saṃvāsena, bhikkhave, sīlaṃ veditabbaṃ, tañca kho dīghena addhunā, na ittaraṃ; manasikarotā, no amanasikarotā; paññavatā, no duppaññenā’ti, iti yaṃ taṃ vuttaṃ idametaṃ paṭicca vuttaṃ.

That’s why I said that you can get to know a person’s ethics by living with them. But only after a long time, not a short time; only when attentive, not when inattentive; and only by the wise, not the witless.