The owner of this café has done well by refusing to sell forbidden substances in his café, such as refusing to sell cigarettes and refusing to allow people to do things that go against Islamic etiquette. May Allaah reward him with good. 

But it remains for him to forbid mixing, because of the evil and temptation that it involves. The Qur’aan and Sunnah indicate that mixing is haraam. For example: 

Allaah says (interpretation of the meaning): 

“And when you ask (his wives) for anything you want, ask them from behind a screen, that is purer for your hearts and for their hearts”

[al-Ahzaab 33:53]

Ibn Katheer (may Allaah have mercy on him) said, commenting on this verse: i.e., just as it is forbidden for you to enter upon them, it is also forbidden for you to look at them at all; even if one of you has a need to ask them for anything, he should not look at them or ask of them except from behind a screen. 

Al-Qurtubi (may Allaah have mercy on him) said: This verse indicates that Allaah has given permission to ask of them from behind a screen in the case of necessity, or when consulting them about some matter. This meaning includes all women, because the basic principle of sharee’ah is that the whole of a woman is ‘awrah. 

And Allaah says (interpretation of the meaning): 

“O wives of the Prophet! You are not like any other women. If you keep your duty (to Allaah), then be not soft in speech, lest he in whose heart is a disease (of hypocrisy, or evil desire for adultery) should be moved with desire, but speak in an honourable manner”

[al-Ahzaab 33:32]

If there is this warning against being soft of speech lest the one in whose heart is a disease be moved with desire, then what about men sitting with women who are clothed yet naked, who go astray and lead others astray, chatting and laughing together, and looking at one another? What fitnah can be greater than that? What heart can remain free of sickness when this is the case? 

The Prophet (peace and blessings of Allaah be upon him) took care to prevent men mixing with women even in the dearest spots on earth to Allaah, namely the mosques, when he separated the rows of men and women, and he stayed for a while after saying the salaam so that the women could depart, and he designated a door of the mosque specifically for women. The evidence for that is as flows: 

1 – It was narrated that Umm Salamah (may Allaah be pleased with her) said: When the Messenger of Allaah (peace and blessings of Allaah be upon him) had said the salaam, the women would get up and leave when they had said the salaam, and he would stay for a while before getting up to leave. Ibn Shihaab said: I think – and Allaah knows best – that he stayed a while so that the women could disperse before the men got up to leave. Narrated by al-Bukhaari, no. 793. 

2 – It was narrated that Ibn ‘Umar (may Allaah be pleased with him) said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Why don’t we leave this door for the women?” Naafi’ said: Ibn ‘Umar never entered through that door until he died. Narrated by Abu Dawood, 462; classed as saheeh by al-Albaani in Saheeh Abi Dawood. 

3 – It was narrated that Abu Hurayrah (may Allaah be pleased with him) said: The Prophet (peace and blessings of Allaah be upon him) said: “The best rows for men are the first ones and the worst are the last, and the best rows for women are the last ones and the worst are the first.” Narrated by Muslim, 664. 

This is among the greatest evidence that Islam forbids mixing. The further away the men are from the women’s rows the better, and the further away the women are from the men’s rows the better. 

If these precautions are to be taken in the mosque which is a pure place of worship, then taking them in other places is undoubtedly more important. 

4 – It was narrated from Abu Usayd al-Ansaari that he heard the Messenger of Allaah (peace and blessings of Allaah be upon him) say, when he was outside the mosque and the men were mixing with the women in the road. The Messenger of Allaah (peace and blessings of Allaah be upon him) said to the women: “Move aside, for you have no right to walk in the middle of the road; you should walk at the sides of the road.” Then a woman would walk so close to the walls that her garment would catch on the wall because she walked so close to it.” Narrated by Abu Dawood, 5272; classed as hasan by al-Albaani in Saheeh Abi Dawood. 

For more details on the dangers of mixing, please see the answer to question no. 1200. 

Since mixing is haraam, the owner of this café is committing sin by allowing it and refraining from denouncing it, and by helping these people to commit sin by providing a place for them where they can disobey Allaah. 

What he has to do is to fear Allaah and not help to spread evil and corruption among the believers. He should be keen to make his food good (i.e., from halaal sources), for “every body that is nourished on haraam, the Fire is more befitting for it,” as the Prophet (peace and blessings of Allaah be upon him) said. Narrated by al-Tabaraani and Abu Na’eem from Abu Bakr; classed as saheeh by al-Albaani in Saheeh al-Jaami’, no. 4519. 

Another version was narrated from Ka’b ibn ‘Ajrah: “No flesh grows that is nourished by haraam but the Fire is more befitting for it.”  

If he can prevent mixing, then this is what he must do, or else he can restrict the café to men only. Otherwise he should look for other, permissible work. Whoever gives up a thing for the sake of Allaah, Allaah will compensate him with something better than it. 

“And whosoever fears Allaah and keeps his duty to Him, He will make a way for him to get out (from every difficulty).

3. And He will provide him from (sources) he never could imagine”

[al-Talaaq 65:2-3]

And Allaah knows best.