Musnad Ahmad 30:1989

Abu Nu'aym narrated to us, he said: Sufyan al-Thawri narrated to us, from 'Abd al-Malik ibn 'Umayr, from Abu Salamah, from Abu Hurayrah, from the Prophet, peace and blessings of Allah be upon him, who said: "The truest word a poet ever spoke is: 'Indeed, everything except Allah is false.' And Umayyah ibn Abi al-Salt was on the verge of becoming a Muslim."