Yiddish: An ass is recognized by his long ears, a fool by his long tongue.

SOURCE: Stutchkoff, Der Oytser fun der Yidisher Shprakh.
A "long tongue" in Yiddish, like a "big mouth" in English, indicates that a person talks a lot.

אַן אייזל דערקענט מען אין די לאַנגע אויערן, אַ נאַר אין דער לאַנגער צונג.

An eyzl derkent men in di lange oyern, a nar in der langer tsung.

An ass is recognized by his long ears, a fool by his long tongue.