(39) CHAPTER. The Statement of Allah: “...And remember Our slave Dawud (David), endued with power. Verily, he was ever oft-returning in all matters and in repentance (toward Allah)... (up to)... And sound judgement in speech and decision. (V.38:17-20)
Narrated Mujahid: I asked Ibn `Abbas, Should we perform a prostration on reciting Surat-Sa`d? He recited (the Sura) including: 'And among his progeny, David, Solomon..(up to)...so follow their guidance (6.84-91) And then he said, Your Prophet is amongst those people who have been ordered to follow them (i.e. the preceding apostles).
Narrated Ibn `Abbas: The prostration in Sura-Sa`d is not amongst the compulsory prostrations, though I saw the Prophet prostrating on reciting it.