三人 寄れば 姦しい

おんな さんにん よれば かしましい

Wherever women gather it is noisy

To understand this kotowaza (play on words) you need the visual aid (I hope your browser displays Unicode). The last word kashimashii (noisy, mischievious) uses the kanji 姦 composed from the radical for woman 女 repeated three times. The rest of the 'pun' comes from the kanji in yoreba (according to, if this is the case). The kanji 寄 has a meaning of "gather" and has a pronunciation of 'yo', so the pun comes from yoreba spelled with the kanji for coming together. A very literal translation would be "Given the case of three women (together) it is noisy."

Put all together you have a nice little joke on the etymology of the kanji in kashimashii which demonstrates some ancient Chinese chauvinism.