Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) wrote a letter to Sayyiduna Abu Ubaydah bin al-Jarrah (may Allah be pleased with him): 'Amma ba'd' (After praise and glorification)! It has reached me that Muslim women bathe in the bathhouses, and women of the People of the Book are with them. So forbid them from that and stand in the way of it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13542
Umar bin al-Khattab (may Allah be pleased with him) wrote a letter to Abu Ubaydah bin al-Jarrah (may Allah be pleased with him): After praise and glorification! It has reached me that Muslim women bathe in the bathhouses with the women of the idolaters. Forbid them from that, for it is not lawful for a woman who believes in Allah and the Last Day that her private parts be seen by anyone except a woman of her own religion (millah).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13543
Mujahid (may Allah have mercy on him) said: A Muslim woman should not take off her head-covering in the presence of an idolatrous woman, nor kiss her, because Allah Almighty said: "or their women" [Surah al-Nur: 31], and these (disbelieving women) are not their women.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13544