I asked Muhajid regarding the prostration in Surat Sa`d. He said, "Ibn `Abbas was asked the same question and he said, 'Those are they (the prophets) whom Allah had Guided. So follow their guidance." (6.90) Ibn `Abbas used to perform a prostration (on reading this Sura).
Sahih al-Bukhari Book 65, Hadith 328
← Previous Hadith The Prophet (ﷺ) said, "He who says that I am better than Jonah bin Matta, tells a lie.'

Sahih al-Bukhari Book 65, Hadith 327 Next Hadith → 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 Messenger (ﷺ) (Muhammad) performed this prostration too.'

Sahih al-Bukhari Book 65, Hadith 329