Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- Islam does not object to events or gatherings where members of the opposite sex are present in the same place as long as all abide by the Islamic teachings and manners. If such gatherings abide by the Shari`ah rulings, then there is nothing wrong with them.
2- What is forbidden is khalwah (seclusion between two members of the opposite sex); tabarruj (revealing women’s attractions and awrahs and all other forbidden acts such as seductive talk or walk); and physical contact between members of the opposite sex.
3- Therefore, if the mixed wedding sticks to these instructions, it is allowed. But if people do not abide by these conditions—which is common nowadays—then the presence of men and women in the same place is unlawful.
Responding to the question you raised, the European Council for Fatwa and Research issued the following fatwa:
The term “mixed” is one which is not used by either the Qur’an or the Sunnah, while most people believe it to be an unquestionable matter in Islam, as though there was something in the Qur’an or in the Hadith of Prophet Muhammad (peace and blessings be upon him) that states clearly that mixed congregations are haram (forbidden). This is one of the grave mistakes which many Muslims commit today, unfortunately.
Our opinion in this matter is that the Islamic Shari`ah did not object to men and women being present in one place on condition that three matters are avoided and refrained from:
Seclusion (khalwah), that is a man and woman meet in a place where no one else can see them.
Adornment of women, that is a woman uncovers what Allah (Mighty and Exalted be He) decreed to be covered of her body, or she wears perfume or jewelry or walks or talks in such a way that draws attention and raises ill-thoughts and feelings.
However, we see that people often do not abide by these conditions in weddings, and thus the presence of men and women in one place becomes unlawful.
Allah Almighty knows best.
Editor’s note: This fatwa is from Ask the Scholar’s archive and was originally published at an earlier date.
Source: Excerpted, with slight modifications, from http://www.ecfr.org