Is it obligatory to say "Bismillah" (Basmalah) before Al-Fatihah and a Surah in prayer, and does its ruling differ between obligatory and supererogatory prayers?

Most scholars are of the view that the Basmalah is a complete verse from the beginning of Surat Al-Fatihah, and the prayer is not valid without reciting it before Al-Fatihah. It must be recited in both obligatory and supererogatory prayers, and in both audible and silent prayers. The Basmalah is recommended when reciting any other surah from its beginning. However, if the worshipper or reciter recites from the middle of a surah, they have the choice to recite it or leave it. It is sunnah to recite the Basmalah silently in audible prayers.