Eating Food of Those Who Sell Wine
30-1-2002 | IslamWeb
Question:
1-I want to know if it is okay if I eat some moslem's food in the mosque and those people sell wine in their stores.
Answer:
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad 
is His slave and Messenger.
As a rule, a Muslim is prohibited from trading in every intoxicant material. The Prophet said: “Allah has prohibited selling wine, dead animals (not slaughtered according to the Sharee’ah), pigs and idols.” Imam As-San'aani 
said: “This Hadeeth indicates that it is forbidden to take the price of something that is forbidden to trade in.” This means that money gained from selling wine is prohibited.
Thus, if one who trades in wine invites some people for food and we know that most of his money is ill-gotten, then we should not respond to his invitation nor eat from his food, and vice-versa [i.e. if most of is money is lawful, then we honor his invitation and eat from his food]. However, we are to advise him with wisdom and good manner.
Allah Says (what means): {Invite to the way of your Lord with wisdom and good instruction, and argue with them in a way that is best...} [Quran 16:125]
If such a person gives up this prohibited business, then it will be good. Yet, we advise him more and more. But if he does not give up such a prohibited business, people who live near him should do their duty to enjoin good and forbid wrong in accordance with the Hadeeth narrated by Abu Sa’eed Al-Khudri 
that 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]
For more benefit on someone whose earnings are mixed between lawful and unlawful, please refer to Fataawa 89599, 264832, 233188, 87211 and 81560.
Allah knows best.