Abu Dawud Book 8, Hadith Number 2526.
Chapter : Not known.
Narated By Anas ibn Malik : The Prophet (PBUH) said: Three things are the roots of faith: to refrain from (killing) a person who utters, “There is no god but Allah” and not to declare him unbeliever whatever sin he commits, and not to excommunicate him from Islam for his any action; and jihad will be performed continuously since the day Allah sent me as a prophet until the day the last member of my community will fight with the Dajjal (Antichrist). The tyranny of any tyrant and the justice of any just (ruler) will not invalidate it. One must have faith in Divine decree.