Musnad Abu Ya'la al-Mawsili 46:6

Harun ibn Ma'ruf narrated to us, Sufyan narrated to us, from Ibn Abi Najih, from his father, from Qays ibn Sa'd, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "If faith were suspended at the Pleiades, men from the sons of Persia would attain it."