Is it permissible to offer ready-made food from a restaurant as expiation for an oath (kaffarat al-yameen), or must it be from the types of food given in Zakat al-Fitr, such as rice?

The expiation for an oath is to feed ten needy persons from the average of what you feed your own families, or to clothe them, or to free a slave. If one cannot find [any of these], then it is to fast for three days. If a Muslim chooses to feed, he may give the needy uncooked food (like a bag of rice), or cooked food, or he may prepare food in his home and invite ten needy persons; all of these are valid and sufficient. This is supported by the fact that what is obligatory in expiations is feeding, not ownership, and this is what is established from the Companions. It is also permissible to give each needy person half a sa' of wheat, rice, or other [staple food], or to provide lunch or dinner for ten needy persons.