All perfect praise be to Allah, The Lord of The Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
If mixing between non-mahram men and women entails gathering in one place without adhering to the rulings and regulations of Islamic Law-there being physical contact between the genders, immodesty in dress or speech, failure to cover one's awrah (private parts), the presence of impermissible seclusion (khulwah), failure to lower the gaze, or the presence of frivolous talk and unnecessary conversation—then it is forbidden.
However, if the gathering is for a considerable religiously acceptable purpose and the Islamic regulations are observed, then there is no sin in it. Both parties—men and women—must observe the following:
1. There must be no impermissible seclusion between a man and a non-mahram woman, according to the saying of the Prophet, peace and blessings be upon him: "A man must never be alone with a woman, for the third [present] is Satan." [Narrated by Al-Tirmidhi]
2. Each party must lower their gaze from the other. Allah the Almighty says {what means}: "Tell the believing men to lower their gaze" [An-Nur/ 30], and He says {what means}: "And tell the believing women to lower their gaze" [An-Nur/31].
3. Both parties must observe covering the awrah and modesty in dress, according to the saying of Allah the Almighty {which means}: "...and not expose their adornment..." and His saying {which means}: And when ye ask (his ladies) for anything ye want, ask them from before a screen "[Al-Ahzab/53].
4. Refraining from jesting, flirtatious speech, and exceeding conventional norms in that, according to the saying of Allah the Almighty {which means}: "... be not too complacent of speech, lest one in whose heart is a disease should be moved with desire..." [Al-Ahzab/32].
In general, Islamic Law has permitted women to go out for congregational prayers and the Eid prayers. It has also permitted them to perform Tawaf and Sa'i during Umrah and Hajj, and to interact with men for buying, selling, leasing, and other transactions. It has permitted them to witness contracts, and to go out with the army for nursing. All of the above involve mixing between men and women. Therefore, acts of worship or daily life activities are not prohibited merely because mixing occurs. Shaykh al-Islam Imam Ibn Hajar al-Haytami, may Allah have mercy on him, said: "Whoever issues a general prohibition of visitation for fear of such mixing would consequently have to generally prohibit acts such as Tawaf and Ramal [The ritual where male pilgrims are required to walk briskly with their chests thrust forward and with their shoulders rolling slightly during the first three circuits of Tawaf ul-Qudum (Arrival Tawaf).], and even standing at Arafah and Muzdalifah, and stoning [the jamarat] if one fears mixing or something similar. Since the Imams did not prohibit any of that, despite it involving the utmost mixing, and they only prohibited the mixing itself and nothing else, the same applies here. Do not be deceived by the opinion of those who condemn visitation for fear of mixing, for their statement must be understood within the details and framework we have established; otherwise, it would be baseless." [Al-Fatawa al-Fiqhiyyah al-Kubra, Vol.2/P.24]
In conclusion, if the aforementioned Shari'ah regulations and conditions are observed, then there is no sin in it, and such mixing is not considered forbidden. And Allah the Almighty knows best.
