The following link quotes a snippet:
A young boy had a dream; ‘In the dream, I saw myself in a huge, flat area. I saw an army mounted on white horses moving towards me. All of them were wearing black turbans. One of the horsemen... had shiny eyes... He moved a flag towards me and said, “Hand this flag over to Imam Mahdi Muhammad bin Abdullah at the gates of Al-Quds (Jerusalem).” I took the flag from him, and I saw that the army started marching behind me.’
So from which primary Islamic book does the above snippet come from and is it authentic, and can this even be called a "hadith"?