Sahih al-Bukhari 6658

Sa'd ibn Hafs narrated to us; Shayban narrated to us, from Mansur, from Ibrahim, from Ubaydah, from Abdullah, who said: The Prophet, peace and blessings be upon him, was asked who the best people were. He said: ‘My generation, then those who follow them, then those who follow them. Then will come people whose testimony precedes their oath, and whose oath precedes their testimony.’ Ibrahim said: When we were boys, our teachers used to forbid us from swearing by testimony or by a covenant.