313.Whoever believes in Allah and the Last Day must not enter the public bath without a lower garment (to cover his private parts), and whoever believes in Allah and the Last Day must not let his wife go to the public bath.
(Nisai, Abu Dawud, Tirmidhi).
(The Lawful and Prohibited in Islam (arb: Al Halal Wal Haram Fil Islam) by. Yusuf Qaradawi).