Musannaf Ibn Abi Shaybah

Hazrat Auf narrates from Hazrat Muhammad bin Sirin, who said: There will be a caliph in this ummah who cannot be given superiority over Abu Bakr and Umar. (The meaning is that in the end times, the signs of piety in this ummah and the spread of justice and fairness among its people will resemble those of the two Shaykhs, otherwise the superiority of the two Shaykhs is definite.)