Taken from : alifta.net
Q 2: There has been heated debate about salat-ul-Tasabih (supererogatory Prayer in which Allah is glorified 75 times in each unit of Prayer). I hope you will shed some light on this.
A: Salat-ul-Tasabih is not Mashru‘ (Islamically prescribed), as the Hadith that it is reported regarding it is not authentically narrated from the Prophet (peace be upon him). It also differs from the prescribed Salahs in regard to its form, words and actions, which is evidence that it is not prescribed. Certainly, the Salahs authentically reported from the Prophet (peace be upon him) are perfectly sufficient to dispense with this strange Salah, which is incompatible with what is known of the Purified Shar‘ (Law).
May Allah grant us success! May peace and blessings be upon our Prophet Muhammad, and his family and Companions!
Permanent Committee for Scholarly Research and Ifta’ Members : Bakr Abu Zayd, `Abdul-`Aziz Al Al-Shaykh, Salih Al-Fawzan, `Abdullah ibn Ghudayyan
Deputy Chairman : `Abdul-Razzaq `Afify
The Chairman : `Abdul-`Aziz ibn `Abdullah ibn Baz