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Traits - Ṭhāna Sutta (AN 4:192) That might be what you're thinking about:
“Monks, these four traits may be known by means of four (other) traits. Which four?
“It’s through living together that a person’s virtue may be known, and then only after a long period, not a short period; by one who is attentive, not by one who is inattentive; by one who is discerning, not by one who is not discerning.
“It’s through dealing with a person that his purity may be known, and then only after a long period, not a short period; by one who is attentive, not by one who is inattentive; by one who is discerning, not by one who is not discerning.
“It’s through adversity that a person’s endurance may be known, and then only after a long period, not a short period; by one who is attentive, not by one who is inattentive; by one who is discerning, not by one who is not discerning.
“It’s through discussion that a person’s discernment may be known, and then only after a long period, not a short period; by one who is attentive, not by one who is inattentive; by one who is discerning, not by one who is not discerning.."
It continues in more detail after that point.