בשלושה דברים אדם ניכר בכוסו בכיסו ובכעסו

Etymology
From the Babylonian Talmud, Eruvin 65. Literally “In three things man is recognized: in his cup, in his pocket, and in his anger” (the three nouns sound similar in Hebrew), or in idiomatic English, “By three things a man is known: by his cup, by his pocket, and by his anger.” (i.e., by how he behaves when drunk, how generous he is with his possessions, and how he behaves when in a temper).

Proverb

 * 1) People reveal their true personality when influenced by drink, money, or anger.