The Rising of the Sun from the West
According to a saying of Prophet Mohammad, the world will not come to an end before the advent of Imam Mehdi and Imam Mehdi will not appear before a sign regarding him appears on the Sun.
Imam Mehdi will not come until a sign regarding Him appears on the Sun. [ Imam Jafar Sadiq ]
The Mehdi will not emerge until a sign emerges from the Sun. [ Al-Muttaqi al-Hindi’ s book Al-Burhan fi Alamat al-Mahdi Akhir al-Zaman, p. 33 ]