Awwam bin Hawshab says: I asked Mujahid about the prostration (sajdah) in Surah Sad. He replied: Yes, it is a prostration. And I had asked about it from Sayyiduna Abdullah bin Abbas (may Allah be pleased with him), so he said: Do you recite this verse: {وَمِنْ ذُرِّیَّتِہٖ دَاودَ وَ سُلَیمَانَ}, at the end of which is: {فَبِہُدَاہُمُ اقْتَدِہْ} (O Muhammad! You too follow their guidance). See, your Prophet has been commanded to follow Dawud (peace be upon him).