Musnad Ahmad 26:580

'Abd al-Rahman narrated to us, he said: Sufyan narrated to us, from Mansur, from Ibrahim, from 'Ubaydah, from 'Abdullah, from the Prophet, may Allah bless him and grant him peace, that he said: "The best of people are my generation, then those who follow them, then those who follow them"—three or four times—"then a people will come whose testimony precedes their oath, and their oath precedes their testimony." He said: And our companions used to beat us when we were young boys regarding testimony and covenants.