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 'alyhi wa sallam, is His slave and Messenger.
The Faatih prayer that you mentioned was not narrated on the authority of the Prophet, sallallaahu ‘alayhi wa sallam, in any authentic or even weak Hadeeth, and it does not exist in any of the Sunnah books: neither Al-Muwatta’, Al-Bukhari or any other book. As a matter of fact, this prayer was invented by some heretic innovators who exaggerated when describing its merits, to the extent that it made them prefer it to the Quran.
The Tijaaniyyah followers claim that their leader Ahmad At-Tijaani, who died in 1230 AH (1815 CE), met the Prophet, sallallaahu ‘alayhi wa sallam, personally and learnt this prayer from him. Moreover, they claim that saying this prayer once is equal to reciting the Quran six times. They claim, furthermore, that the Prophet, sallallaahu ‘alayhi wa sallam, informed At-Tijaani that saying this prayer once is equal to reciting all kinds of Athkaar (mentionings), supplications and the entire Quran six thousand times.
Actually, by saying this they are making the Quran an object of ridicule and encouraging people to stop reciting the Quran, the very thing that will make people easily respond to their follies and misleading claims. These people tell lies about Allaah The Almighty, and claim that this prayer is from His words and revealed by the Power and Will of Allaah. This is not true, of course, for how could it be so if it is not mentioned in any of the Sunnah books and the Prophet, sallallaahu ‘alayhi wa sallam, did not teach it to any of his companions? Supposing, for argument’s sake, that this prayer is indeed from the words of Allaah The Almighty, then why would saying it once be better than reciting the entire Quran six thousand times? This can never be said by someone who truly knows the great value of the Holy Quran.
Moreover, followers of the Tijaaniyyah sect claim that reciting this prayer once expiates one’s sins. This is definitely a lie that is meant to mislead those who are seduced by this sect. Not only this, but At-Tijaani also claimed that whoever sees him will enter Paradise and that he alone can admit all his companions to Paradise without reckoning or punishment, no matter how many sins they commit. How can this be true if the Prophet, sallallaahu ‘alayhi wa sallam, himself was not granted this privilege? Instead, he, sallallaahu ‘alayhi wa sallam, mentioned that some of his companions will be held back from the Hawdh (Basin) on the Day of Judgment, besides the fact that some Muslims will certainly enter Hell and be brought out by the Prophet’s, sallallaahu ‘alayhi wa sallam, intercession, as acknowledged by Ahlus-Sunnah Wal-Jamaa‘ah (the mainstream Sunni majority).
Allaah Knows best.