Is there a Prayer known as Salatul-Fa'idah?

Question :

Some people say that there is a prayer known as Salatul-Fa'idah which consists of a hundred Rak'ahs; and it is also said that it is four Rak'ahs which are prayed in the last Friday of Ramadhan. Is this saying correct, or is it an innovation?

Answer:

This saying is not correct, and there is no prayer called Salatul-Fa'idah all of the prayers are beneficial, the obligatory prayers being the most beneficial, because any act of worship, if it is obligatory, is better than the supererogatory, according to what has been authentically reported in the authentic Hadith which states that Allah, the Most High says:
My servant does not draw near to Me by anything more than that which I have enjoined upon him.

And because Allah has made them obligatory, this is a proof that He loves them and that they are more beneficial for the worshipper than the non-obligatory prayers, and this is why they were enjoined upon him so that he may earn their reward. So all of the prayers are beneficial. But as for a particular prayer which is called Salatul-Fa'idah, it is an innovation without any basis, and a person should beware of remembrance and prayers which spread among the people and which are completely without basis in the Sunnah. It should be known that essentially all acts of worship are forbidden except those which have been legislated. Therefore, it is not permissible for a person to worship Allah by any means which has not been legislated by Allah in His Book or the Sunnah of His Messenger. And when a person is in doubt whether something is an act of worship or not, (he should know that) it is not an act of worship unless there is some evidence to prove that it is so. And Allah knows best.

Source:
Ibn 'Uthaimin
Fatawa Islamiyah, Vol. 2 Pages 313-314