Musnad Ahmad 790:138

'Affan and Bahz narrated to us, they said: Abu 'Awanah narrated to us, Qatadah narrated to us. Bahz said: From Qatadah, from Zurarah ibn Awfa, from 'Imran ibn Husayn, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The best of my nation is the generation in which I was sent, then those who follow them, then those who follow them." He said: "And I do not know if he mentioned the third or not." "Then a people will arise who will bear witness without being asked to bear witness, and they will make vows but not fulfill them, and they will betray and will not be trusted, and obesity will spread among them."