Musnad Ahmad 569:1

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from Ibn Tawus, from 'Ikrimah ibn Khalid, from al-Muttalib ibn Abi Wada'ah, who said: "I saw the Messenger of Allah (peace and blessings of Allah be upon him) prostrate in [Surah] al-Najm, and the people prostrated with him." Al-Muttalib said: "And I did not prostrate with them, and he was a polytheist on that day." Al-Muttalib said: "So I will never abandon the prostration in it ever."