All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
A Muslim is ordered to seek what is lawful and pure in what he eats, drinks, and wears, and in his dwelling…etc. Abu Hurayrah narrated that the Prophet said: "Allaah is Tayyib (i.e. pure and good) and does not accept but that which is good and pure." [Muslim] Allaah, the Most High, ordered the believers of the same thing which He ordered the Prophets; Allaah Says (what means): {O (you) Messengers! Eat of the Tayibat [all kinds of Halal a (legal) foods which Allâh has made legal (meat of slaughtered eatable animals, milk products, fats, vegetables, fruits, etc.], and do righteous deeds….}[Quran 23: 51]. Allaah also Says (what means): {O you who believe (in the Oneness of Allaah - Islamic Monotheism)! Eat of the lawful things that We have provided you with,… }[Quran 2: 172]
Then he (the Prophet ) mentioned a disheveled, dusty man who extends his travel and raises up his hands to the sky (in supplication saying): "O Lord! O Lord!" although his food is Haram, his drink is Haram, his clothes are Haram and he is fed with Haram. So, how could the supplication (of such a man) be responded to?"
As regards a person whose lawful money is mixed with unlawful earnings, the scholars differed in opinion in regard to the permissibility of consuming from his money or accepting his donation or gift. Some scholars believe that this is absolutely lawful. Others believe that it is absolutely unlawful. A third group of scholars made some distinctions. They said: If the majority of his money is lawful (Halal) there is no objection to eat at his home and deal with him as the rule is established according to the majority. But if the majority of his money is Haram (forbidden) some scholars dislike eating from his meal or accepting his donation or gift. Others even forbid that. This is in the case there is ambiguity and the money is mixed from what is lawful and what is unlawful. But if it is clear for us that the food itself or the gift itself is absolutley lawful or absolutely unlawful, then there is no problem as the ruling that is applied in this case is according to the principle.
Allaah Knows best.