Sahih al-Bukhari — Hadith 1,882

Allah's Messenger (ﷺ) told us a long narrative about Ad-Dajjal, and among the many things he mentioned, was his saying, "Ad-Dajjal will come and it will be forbidden for him to pass through the entrances of Medina. He will land in some of the salty barren areas (outside) Medina; on that day the best man or one of the best men will come up to him and say, 'I testify that you are the same Dajjal whose description was given to us by Allah's Messenger (ﷺ) .' Ad-Dajjal will say to the people, 'If I kill this man and bring him back to life again, will you doubt my claim?' They will say, 'No.' Then Ad-Dajjal will kill that man and bring him back to life. That man will say, 'Now I know your reality better than before.' Ad-Dajjal will say, 'I want to kill him but I cannot.' "