On Consuming the Food of Muslims with Unlawful Income

Answered by Sayyidi al-Ḥabīb `Umar bin Hafīẓ (may Allāh preserve him and benefit us by him).

Is it permissible to eat the food of Muslims who have some unlawful income from selling alcohol or other prohibited things?

It is permissible as long as you do not know for sure that the food has been purchased with money from an unlawful source and you know that they have income from lawful sources. However, it is better out of scrupulousness to avoid eating such food.