Musnad Ahmad 32:184

Yahya narrated to us, from Uqbah ibn Ubayd al-Ta’i, Bashir ibn Yasar narrated to me, he said: Anas came to Medina, and we said to him: "What have you disapproved of us since the time of the Prophet of Allah, may Allah bless him and grant him peace?" He said: "I have not disapproved of anything from you, except that you do not straighten your rows."