Is it permissible to eat from the food offered at Mawlid (the Prophet's Birthday) celebrations where the "Salat al-Nariya" (Prayer of Fire) is recited, knowing that these practices are innovations? And what is the evidence for the impermissibility of eating from it?

Celebrating the Mawlid (Prophet's Birthday) is an innovation (bid‘ah), and it is impermissible to hold such celebrations. It is also impermissible to eat from what is prepared for and during it, as it constitutes cooperation in sin and transgression. The "Salat al-Nariya" (Fire Prayer) is among the innovated prayers of the Sufis, so it is impermissible to attend its gatherings or participate in them.