Imam Malik's Muwatta, Chapter: Business Transactions

Yahya related to me from Malik from Ibn Shihab from Abu Bakr ibn Abd ar-Rahman ibn al-Harith ibn Hisham from Abu Masud al-Ansari that the Messenger of Allah, may Allah bless him and grant him peace, forbade the sale price of a dog, the earnings of a prostitute and the earnings of a fortune teller. By the earnings of a prostitute he meant what a woman was given for fornication. The earnings of a fortune teller were what he was given to tell a fortune. Malik said, "I disapprove of the price of a dog, whether it is a hunting dog or otherwise because the Messenger of Allah, may Allah bless him and grant him peace, forbade the price of a dog."