Sahih Bukhari Volume 5, Book 57, Hadith Number 3.

Narated By Abdullah : The Prophet said, “The best people are those living in my generation, and then those who will follow them, and then those who will follow the latter. Then there will come some people who will bear witness before taking oaths, and take oaths before bearing witness.” (Ibrahim, a sub-narrator said, “They used to beat us for witnesses and covenants when we were still children.”)