Musnad Abu Ya'la al-Mawsili 110:96

'Ali ibn al-Ja'd narrated to us, Shu'bah informed us, from 'Amr ibn Murrah, who said: I heard Yahya ibn al-Jazzar, from Ibn 'Abbas, who said: I came with a boy from Banu Hashim on a donkey, and we passed in front of the Prophet (may Allah bless him and grant him peace) while he was praying. We dismounted from it and left the donkey to eat from the herbs of the earth—or he said: from the vegetation of the earth—and we entered into the prayer with him. A man said: "Was there a staff (anazah) in front of him?" He said: "No."