How sound is what is said about the prayer of "the Orphan Friday" that expiates eighty months (of sins)? Did Ali (may Allah be pleased with him) pray it? Is it considered a bid'ah hasanah (a good innovation)?

What is known as "Orphan Friday," which is the last Friday of Ramadan, and the beliefs associated with it have no basis in Islamic law. There is no difference between it and the other Fridays of the month. No special prayer has been reported concerning it, nor is it reported that Ali (may Allah be pleased with him) performed this prayer. Designating it for a specific act of worship or gathering is considered an additional innovation (bid'ah idafiyyah). Al-Shawkani mentioned that the hadith: "Whoever prays on the last Friday of Ramadan the five obligatory prayers of the day and night, it will atone for any deficiencies in his prayers during the year" is undeniably fabricated.