What did the Prophet Muhammad (saw) say regarding women attending religious gatherings if they don't have a veil?
 Narrated Hafsa:                     (On `Id) We used to forbid our virgins to go out (for `Id prayer). A lady came and stayed at the Palace of Bani Khalaf. She mentioned that her sister was married to one of the companions of Allah's Apostle who participated in twelve Ghazawats along with Allah's Apostle and her sister was with him in six of them. She said, "We used to dress the wounded and look after the patients." She (her sister) asked Allah's Apostle , "Is there any harm for a woman to stay at home if she doesn't have a veil?" He said, "She should cover herself with the veil of her companion and she should take part in the good deeds and in the religious gatherings of the believers." When Um 'Atiyya came, I asked her. "Did you hear anything about that?" Um 'Atiyya said, "Bi Abi" and she never mentioned the name of Allah's Apostle without saying "Bi Abi" (i.e. 'Let my father be sacrificed for you'). We asked her, "Have you heard Allah's Apostle saying so and so (about women)?" She replied in the affirmative and said, "Let my father be sacrificed for him. He told us that unmarried mature virgins who stay often screened or unmarried young virgins and mature girls who stay often screened should come out and take part in the good deeds and in the religious gatherings of the believers. But the menstruating women should keep away from the Musalla (praying place)." I asked her, "The menstruating women?" She replied, "Don't they present themselves at `Arafat and at such and such places?"