Sahih Muslim
The Book Pertaining to the Merits of the Companions (Allah Be Pleased With Them) of the Holy Prophet (May Peace Be Upon Him) (Kitab Al-Fadail Al-Sahabah)
Book Number: 031 / Hadith Number: 6177
Abu Huraira reported Allah's Messenger (may peace be upon him) as saying: If the din were at the Pleiades, even then a person from Persia would have taken hold of it, or one amongst the Persian descent would have surely found it.