Musannaf Ibn Abi Shayba 27:118

Aswad ibn Amir narrated to us, from Mahdi ibn Maymun, from Muhammad ibn Abd Allah ibn Abi Ya’qub, from al-Hasan ibn Sa’d, from Abd Allah ibn Ja’far, who said: The Prophet, may Allah bless him and grant him peace, made me ride behind him one day. He whispered a hadith to me that I would not tell to anyone among the people. Among the things that the Prophet, may Allah bless him and grant him peace, liked to use for concealment when relieving himself was a mound or a palm-tree enclosure. He entered a palm-tree enclosure of the Ansar one day and saw a camel in it. When the camel saw him, it groaned and its eyes shed tears. He said: So the Prophet, may Allah bless him and grant him peace, wiped its hump and the back of its ears, and it became calm. He then said: "Who does this camel belong to?" or "Who is the owner of this camel?" A man from the Ansar said: "It is mine, O Messenger of Allah." He said: "Show kindness to it, for it has complained to me that you starve it and tire it out."