Musnad Ahmad 32:2111

'Affan narrated to us, Hammad narrated to us, he said: Thabit informed us, from Anas ibn Malik, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "I have been caused to fear for the sake of Allah, and no one is caused to fear [as I have]. And I have been harmed for the sake of Allah, and no one is harmed [as I have]. And there came upon me thirty days and nights, while neither I nor Bilal had any food that a living creature could eat, except for something that Bilal’s armpit could conceal."