Sahih Bukhari Volume 006, Book 060, Hadith Number 156.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 60. Prophetic Commentary on the Qur'an (Tafseer of The Prophet (PBUH))
Narrated By Mujahid : That he asked Ibn 'Abbas, "Is there a prostration Surat-al-Sad?" (38.24) Ibn Abbas said, "Yes," and then recited: "We gave... So follow their guidance." (6.85,90) Then he said, "He (David) is one them (i.e. those prophets)." Mujahid narrated: I asked Ibn 'Abbas (regarding the above Verse). He said, "Your Prophet (Muhammad) was one of those who were ordered to follow them."