Sheikh Sâlih al-Fawzân
When it comes to accepting food and gifts from those who have unlawful wealth, there is a distinction to be made between stolen wealth and wealth acquired by way of unlawful business practices.
The difference is that stolen wealth is decreed as unlawful on account of it being the right of someone else. The thief must restore it to its rightful owner. In a case where a person knows that the thing being given to him is stolen, he should not accept it for this reason, since it should be returned to its rightful owner.
Interest earnings and the like are unlawful because of the way they have been earned. The Prophet (peace be upon him) partook of the wealth of the Jews, though Allah says about them: “And they partook of usury, though they were forbidden from doing so.” [Sûrah al-Nisâ’: 161]
And Allah knows best.
Source: Islam Today