Sahih Bukhari Volume 005, Book 057, Hadith Number 002.

Narated By Imran bin Husain : "Allah's Apostle said, 'The best of my followers are those living in my generation (i.e. my contemporaries). and then those who will follow the latter" 'Imran added, "I do not remember whether he mentioned two or three generations after his generation, then the Prophet added, 'There will come after you, people who will bear witness without being asked to do so, and will be treacherous and untrustworthy, and they will vow and never fulfill their vows, and fatness will appear among them."