Musnad Ahmad 2:78

'Amr ibn al-Haytham narrated to us, Shu'bah narrated to us, from Simak ibn Harb, from al-Nu'man ibn Bashir, from 'Umar, who said: I have seen the Messenger of Allah, peace and blessings of Allah be upon him, writhing, not finding enough of the poor-quality dates to fill his stomach.