Musnad Ahmad 435:81

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Abu al-Tayyah, who said: I heard Humran ibn Aban narrating from Mu'awiyah, who said: "You perform prayers that we accompanied the Messenger of Allah, may Allah bless him and grant him peace, and we never saw him performing them, and he indeed forbade them," meaning the two rak'ahs after the 'Asr prayer.