What evidence did Prophet Muhammad (peace be upon him) have to follow that had him prostrate when reciting Surat Sa`d?
 Narrated Al-Awwam:                     I asked Mujahid regarding the prostration in Surat Sa`d. He said, "I asked Ibn `Abbas, 'What evidence makes you prostrate?' He said, "Don't you recite:--'And among his progeny, David and Solomon..(6.84). Those are they whom Allah had guided. So follow their guidance.' (6.90) So David was the one of those prophets whom Prophet (Muhammad) was ordered to follow. David prostrated, so Allah's Apostle (Muhammad) performed this prostration too.'