What is the ruling on celebrating the fifth of Sha'ban, known as "Sayyidi Shahin," by dedicating certain foods to it, such as mushabbak and popcorn? Is it considered an innovation (bid'ah) or a custom ('adah)?

It is not permissible to celebrate the fifth day of Sha'ban with what is called (Sayyidi Shahin); because singling out a day for Muslims to celebrate, other than the two Eids of Fitr and Adha and Friday, is an innovation in religion. The veneration of days and gathering on them in a customary manner is dependent on what Allah and His Messenger have legislated, and it is part of religion and rituals. Allah has substituted for the Muslims the two days of ignorance with the two days of Adha and Fitr. If there were other days to be venerated, the Prophet, peace and blessings be upon him, would have informed us of them. So, any Eid other than the two Eids of Fitr and Adha is an innovation, and the Prophet, peace and blessings be upon him, said: "Whoever innovates into this affair of ours that which is not from it will have it rejected."