Musannaf Ibn Abi Shayba 3:488

Abu Bakr narrated to us, he said: Sufyan ibn ‘Uyaynah narrated to us, from al-Zuhri, from ‘Ubayd Allah, from Ibn ‘Abbas, who said: I and al-Fadl came upon a female donkey while the Prophet (peace and blessings of Allah be upon him) was leading the people in prayer. We passed by a part of the row, then we dismounted and left it to graze, and he did not say anything to us.