Musnad Ahmad 482:27

Ali ibn Ishaq narrated to us, Ibn al-Mubarak Abdullah informed us, he said: Musa ibn Ali narrated to us, he said: I heard my father saying: I heard Uqbah ibn Amir saying: The Messenger of Allah, may Allah bless him and grant him peace, said: "Learn the Book of Allah, and maintain it, and recite it melodiously; for by Him in Whose hand is my soul, it is more prone to escape than the hobbled camel from its tether."