Musnad Ahmad 110:4

Yahya ibn Sa'id narrated to us, from 'Abd al-Hamid, who said: My father narrated to me, from Tamim ibn Mahmud, from 'Abd al-Rahman ibn Shibl, who said: I heard the Messenger of Allah (may Allah bless him and grant him peace) forbidding three things: the pecking of the crow, the spreading of the beast of prey, and that a man should designate a specific place in the mosque as his own, just as a camel designates its place.