Musannaf Ibn Abi Shayba 13:2118

Abu Bakr narrated to us, he said: Waki' narrated to us, he said: Ibn Abi Dhi'b narrated to us, from Muslim al-Khayyat, who said: I used to buy date pits, fruit stones, and tree leaves for Sa'id ibn al-Musayyib, and he would hoard them.