Suppose person A giving money to B bcz of an innovatory festival the former has celebrated. Is it allowed for B to give that money in charity ?

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, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

If the gift was something which is lawful in itself, then it is permissible to accept it from the donor even if this was at an innovative occasion while not approving the innovation.

Hence, the person to whom the gift was given becomes the owner of it, so it becomes permissible for him to benefit from it by gifting it or using it for other permissible matters.

Shaykh Ibn Taymiyyah said in his book entitled: “Iqtidhaa’ As-Siraat Al-Mustaqeem” while speaking about the festivals of the non-Muslims and their gifts on these festivals: “As regards accepting gifts from them on the day of their festival, indeed, we have already mentioned that ‘Ali Ibn Abi Taalib was given a gift on Nayrooz (a festival of the non-Muslims) and he accepted it.”

Then, he said: “All this is evidence that the festival does not lead to the prohibition of accepting their gift; rather, its ruling on their festival or days other than their festival is alike, as this is not considered as helping them in their non-Muslim rituals.”

Based on this, since accepting gifts from non-Muslims is permissible even if they are gifts of food (as long as the food itself is permissible) that are especially prepared for their Kufr [disbelief] and polytheistic beliefs, then the gift the questioner is asking about is permissible with greater reason.

Allaah Knows best.