Musnad Abu Ya'la al-Mawsili 152:72

Abu Khaythama narrated to us, Jarir narrated to us, from Mansur, from Ibrahim, from Ubaydah al-Salmani, from Abdullah, who said: The Messenger of Allah (ﷺ) was asked: "Which of the people are best?" He said: "My generation, then those who follow them, then those who follow them. Then a people will come whose testimony precedes their oath, and whose oath precedes their testimony." Ibrahim said: "They used to forbid us, while we were young boys, from making covenants and giving testimonies."