Musnad Ahmad 22:26

'Abd al-Razzaq narrated to us, Ibn Jurayj informed us, Muhammad ibn 'Umar ibn 'Ali narrated to me, from al-Fadl ibn 'Abbas, who said: "The Prophet, peace and blessings of Allah be upon him, visited al-'Abbas while we were in a desert of ours. He stood to pray—he said: I think he said: 'Asr—and in front of him was a small dog of ours, and a donkey grazing, with nothing between him and them to act as a barrier between him and them."