Assalamu Alikum.
There are many traditions today that held in some muslim countries and many "religious practices" which are practiced by some muslims but which are wrong, and are mere INNOVATIONS. I'm speaking here about those ceremonies which are held to celebrate every year a day in which a person who's said to be "Wali Salih" (a good servant of Allah) died or was born. It's clear that such things are forbidden and noly lead to "Shirk" waliyadou billah and that's unquestionable.
My question is:
Is it ok for someone to eat the food which was brought from that place without having any intention of asking for it, or going there to get it.But which was brought by someone else, or should it be thrown away and not used?
Jazakom Allaho khairan
May Allah guide us all to the right path.
Assalmo alikum

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.

There is no doubt that these celebrations are innovations and they may lead to extol the dead people, and this could be a means to worship them beside Allaah; for more benefit, please refer to Fatwa 89014.

The animals that are slaughtered on such occasion are also an innovation. As regards eating from these animals, the ruling differs according to the circumstance. For instance, it is not permissible to eat from it if the one who slaughters it does so with the intention of getting closer to other than Allaah, this is whether he mentions the Name of Allaah when he slaughters or a name of other than Allaah, because he intended it in principle for other than Allaah. Allaah Says (what means): {He has only forbidden to you dead animals, as blood, the flesh of swine, and that which has been dedicated to other than Allaah.}[Quran 16:115]  

However, if the person who slaughters the animal does so just for the celebration, and he slaughters it for the Sake of Allaah and utters the Name of Allaah when he slaughters, and intends to distribute it among the poor and needy and so forth, then despite this being an innovation, it does not mean that it is forbidden to eat from it because it was not slaughtered for other than Allaah. So it remains on the principle that it is permissible to eat from it unless something which necessitates the prohibition is confirmed. Of course, these details are about the food which include meat, but if it does not include any meat and it is permissible in principle, then it is permissible to eat from it in any case. However, if a person refrains from eating from it as to deter the person who does the innovation of celebration from doing it, then this is a good thing to do.

Allaah Knows best.