Musnad Ahmad 28:244

Abu Bakr al-Hanafi narrated to us, Usamah ibn Zayd narrated to us, from ‘Amr ibn Shu‘ayb, from his father, from his grandfather: That the Messenger of Allah (peace and blessings of Allah be upon him) was sleeping, and he found a date under his side. He took it and ate it. Then he began to toss and turn during the latter part of the night, and some of his wives were alarmed by that. He said: "I found a date under my side and I ate it, and I feared that it might be from the dates of the charity (sadaqah)."