All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions. Here in US we are renting a place as a Musjid and the ones who run it want it to be according Sunnah. Men pray in front and women pray in the back without a barrier. Some of our sisters come to the Musjid without Hejab, and some even expose too much of their bodies. Sometimes, we have no idea we are in a night club or in Musjid. When we want to say something, they are telling us that do not come to this Musjid. And this is the only Musjid close to our house. We have no idea what to do? Would you please advise us what should we do? Jaza Kum Allah Khair.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

We have already clarified in Fatwa 88708 that it is permissible to put a barrier and separate between men and women in the mosque. This matter is even more confirmed if the situation is as you mentioned in the question, and that some women do not abide by the Hijab, which could cause men to be tempted by them. Therefore, you have the right to object about this matter as this is among forbidding evil, and the Prophet said: "Whoever amongst you sees an evil, he should change it with his hand (i.e. physically), if he is unable he should change it with his tongue (i.e. verbally) and if he is unable, he should change it with his heart (by detesting it in his heart) and that is the weakest level of faith." [Muslim]

The people in charge of that mosque are obliged to fear Allaah and fulfil their religious obligation of ordering women to wear Hijab and reminding them of Allaah. If these women accept, then that is what is required; otherwise they should be prevented from entering the mosque. Of course, it is more appropriate to prevent these women than it is to say to men who object: "do not come to the mosque". How can a man who is obliged to perform his prayer with the congregation in the mosque be told not to come to the mosque, whereas women who are not obliged to perform the prayer in the mosque, and who are not abiding by the Hijab, are not told not to come to the mosque?

Furthermore, it should be noted that a woman is obliged to cover her body even when performing the prayer, except her face and hands. If she performs the prayer while exposing her hair or feet, her prayer is void. For more benefit in this regard, please refer to Fataawa 88862 and 88563.

Therefore, if the women whom you mentioned in the question perform the prayer while exposing their hair or other parts of their body, then their prayer is void. For more benefit on the characteristics of Hijab, please refer to Fataawa 84763 and 83702.  

Finally, we advise you to endeavour to advise and remind the mosque administration in soft words and in a good manner so that they would take the appropriate procedures to prevent men from being tempted by women in the mosque. You may also show them this very Fatwa.

We also advise you and other brothers to admonish the women to abide by the Hijab with its religious characteristics by distributing tapes and books on the subject.