Musnad Ahmad 31:36

'Abd al-Rahman—who is Ibn Mahdi—narrated to us, Malik narrated to us, from Dawud ibn al-Husayn, from Abu Sufyan, from Abu Sa'id al-Khudri: "That the Messenger of Allah, may Allah bless him and grant him peace, forbade al-muzabanah and al-muhaqalah. Al-muzabanah is the buying of fruit on the tops of palm trees with dates by measure. Al-muhaqalah is the renting of land."