Sahih al-Bukhari Book 61, Hadith 113
The people used to ask Allah's Messenger (ﷺ) about good, but I used to ask him about evil for fear that it
might overtake me. Once I said, "O Allah's Messenger (ﷺ)! We were in ignorance and in evil and Allah has
bestowed upon us the present good; will there by any evil after this good?" He said, "Yes." I asked,
"Will there be good after that evil?" He said, "Yes, but it would be tained with Dakhan (i.e. Little
evil)." I asked, "What will its Dakhan be?" He said, "There will be some people who will lead
(people) according to principles other than my tradition. You will see their actions and disapprove of
them." I said, "Will there by any evil after that good?" He said, "Yes, there will be some people who
will invite others to the doors of Hell, and whoever accepts their invitation to it will be thrown in it
(by them)." I said, "O Allah's Messenger (ﷺ)! Describe those people to us." He said, "They will belong to us
and speak our language" I asked, "What do you order me to do if such a thing should take place in my
life?" He said, "Adhere to the group of Muslims and their Chief." I asked, "If there is neither a group
(of Muslims) nor a chief (what shall I do)?" He said, "Keep away from all those different sects, even if
you had to bite (i.e. eat) the root of a tree, till you meet Allah while you are still in that state."
I was with Marwan and Abu Huraira and heard Abu Huraira saying, "I heard the trustworthy, truly inspired one (i.e. the Prophet (ﷺ) ) saying, 'The destruction of my followers will be brought about by the hands of some youngsters from Quraish." Marwan asked, "Youngsters?" Abu Huraira said, "If you wish, I would name them: They are the children of so-and-so and the children of so-and-so."
My companions learned (something about) good (through asking the Prophet) while I learned (something about) evil.