Q. Can one recite more than one Surah in one Rakaat of a Fardh Salaah?
A. When performing a Fardh Salaah, it is preferred for one to not lengthen the Salaah by reciting more than one Surah in a single Rakaat. If more than one Surah is recited in a single Rakaat of Fardh Salaah, it will not affect the validity of the Salaah in any way.
Ideally, this should be done when one is performing their own Sunnah or Nafl Salaah individually. (Fataawa Mahmoodiyyah 7/90)
Allah Ta’ala Knows Best
Mufti Ismaeel Bassa