Malik related to me from Nafi from Ibn Umar that the Messenger ofAllah, may Allah bless him and grant him peace, said, "No one shouldmilk someone else's cow without his permission. Would any of you likesomeone to come to his apartment, break into his larder, and take hisfood? The udders of cows guard their food for their owners, so no oneshould milk someone else's cow without his permission."
USC-MSA web (English) reference: Book 54, Hadith 17
Arabic reference: Book 54, Hadith 1782