The Messenger of Allah ﷺ said, "The best of my nation is the generation among whom I was sent, then those who follow them, then those who follow them." Allah knows best whether he mentioned the third or not. "Then there will appear people who give testimony without being asked to testify, who make vows but do not fulfill them, who betray trusts and cannot be relied upon, and obesity will spread among them."
حدثنا عمرو بن عون قال أنبأنا ح و حدثنا مسدد قال حدثنا أبو عوانة عن قتادة عن زرارة بن أوفى
قال رسول الله ﷺ خير أمتي القرن الذين بعثت فيهم ثم الذين يلونهم ثم الذين يلونهم والله أعلم أذكر الثالث أم لا ثم يظهر قوم يشهدون ولا يستشهدون وينذرون ولا يوفون ويخونون ولا يؤتمنون ويفشو فيهم السمن
Muslim narrated it in the Book of the Virtues of the Companions, chapter on the merit of the Companions, then those who follow them, then those who follow them, hadith no. 2535, from the hadith of Abu Awana with this wording. Bukhari also narrated it, hadith no. 2651, through another route from Imran bin Husayn with this wording.