Musnad Ahmad 1304:15

Abu al-Nadr narrated to us, Abu Mu'awiyah—meaning Shayban—narrated to us, from Layth, from Shahr ibn Hawshab, from Asma bint Yazid, who said: I was holding the rein of al-Adba'—the she-camel of the Messenger of Allah, may Allah bless him and grant him peace—when the entire Surah al-Ma'idah was revealed to him. It nearly broke the forearm of the she-camel due to its weight.