Musannaf Ibn Abi Shayba 13:2170

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Shu’bah narrated to us, from ‘Abd al-Malik ibn ‘Umayr, from al-Mughirah ibn Shu’bah, who said: Ibn ‘Umar was asked about the selling of grapes. He said: "Turn them into raisins, then sell them."