Musnad Ahmad 30:1270

'Abd al-Samad narrated to us, al-Qasim ibn al-Fadl narrated to us, my father narrated to me, from Mu'awiyah al-Mahri, who said: Abu Hurayrah said to me: "O Mahri, the Messenger of Allah (may Allah bless him and grant him peace) forbade the price of a dog, the earnings of a cupper, the earnings of a prostitute, and the earnings of the stud-fee of a stallion."