What is the ruling on the following: Working with a person whose provision is Haraam and eating his food during occasions?
If it is ascertained that all his wealth is haraam, it is not permissible to eat (his food). But if some haraam enters his wealth and there is also some halaal in it, there is no harm eating (his food) because you do not know whether the food is from the halaal or haraam aspect of his wealth. The basis of this affair is that it is allowed to eat InshaaAllaah because the Prophet (sallal-laahu-alayhi-wasallam) ate from the food of the Yahood.
[Source: Fadaa’il al Amaal’ page: 7; by Shaikh Muhammad Bin Abdillaah As-Subayyil (rahimahullaah)]