Musnad Ahmad 30:2315

'Abd al-Wahhab ibn 'Ata narrated to us, 'Awf informed us, from Shahr ibn Hawshab, who said: Abu Hurayrah said: The Messenger of Allah, peace and blessings of Allah be upon him, said: "If knowledge were at the Pleiades, men from the sons of Persia would reach it."