Mixing is Forbidden
Question :
Here in Britain, a meeting is held in one of the schools for the parents and guardians of the students, which is attended by men and women. Is it permissible for the Muslim woman to attend this meeting without a Mahram, when there are men present, bearing in mind that one brother says that it is permissible, citing as evidence the Hadith of Abu Hurairah, may Allah be pleased with him, recorded in Sahih Al-Bukhari and Sahih Muslim, in which it is mentioned that a man came to the Prophet and he requested someone to take him in as a guest, so a man from among of the Ansar took him in as a guest and he mentioned that the Ansari man and his wife sat with him and they showed him that they were eating. I request enlightenment in this matter.
Answer:
In this matter. it is apparent from the question that there is mixing of men and women. Mixing of men and women leads to trial and temptation (Fitnah) and evil and it is, in my opinion, not allowed.
However, if there was a need for the presence of women with men, then it is a must that the women be placed on one side and the men on the other, and that the women wear the Islamic Hijab, so that their bodies are completely covered, even their faces. As for the Hadith which the questioner mentioned, there is no mixing (of the sexes) in it, for the man was only with his wife in one part of his house, while the guest was in the guest quarters.
However, the matter of the Hijab is well known: It was not one of the foremost matters regarding the legislation; it was only legislated about five or six years after the migration of the Prophet and no Hadith has been narrated in which it appears that the Hijab was not worn, therefore it must be understood that this was before the Verses of the Hijab were revealed.
Source:
Ibn 'Uthaimin
Fatawa Islamiyah, Vol. 5 Pages 139-140