Musnad Ahmad 32:536

Hassan narrated to us, Ibn Lahi'ah narrated to us, Yazid ibn Abi Habib and 'Uqayl ibn Khalid narrated to us, from Ibn Shihab, from Anas ibn Malik: "That the Messenger of Allah, peace and blessings of Allah be upon him, forbade that a man should sell the stud-fee of his horse."