Musannaf Ibn Abi Shayba 13:2531

Abu Bakr narrated to us, he said: Ibn Numayr narrated to us, from Fudayl ibn Ghazwan, he said: Abu Dihqana narrated to me, he said: I was sitting with Abdullah ibn Umar, and he said: A guest came to the Messenger of Allah, may Allah bless him and grant him peace. He said to Bilal: "Bring us some food." Bilal went to two sa's of dates and bought with them one sa' of good dates, and their dates were inferior. The Prophet, may Allah bless him and grant him peace, was pleased with the dates. The Prophet, may Allah bless him and grant him peace, said: "Where did this date come from?" He informed him that he had exchanged two sa's for one sa'. The Messenger of Allah, may Allah bless him and grant him peace, said: "Return our dates to us."