Musnad Ahmad 32:169

Abu Mu'awiyah narrated to us, 'Uqbah ibn 'Ubayd narrated to us, from Bashir ibn Yasar, who said: We said to Anas ibn Malik: "What have you disapproved of our state since the time of the Messenger of Allah, may Allah bless him and grant him peace?" He said: "I have disapproved that you do not straighten the rows."