נכנס יין יצא סוד

Etymology
Literally, "in goes wine, out comes secret". From the tendency of alcoholic beverages to make people more talkative, including when it comes to secrets. Furthermore, the gematria values of the Hebrew words for wine and secret are equal: 60 + 6 + 4 (סוד) = 10 + 10 + 50 (יין).

Proverb

 * 1) in vino veritas