Musnad Abu Ya'la al-Mawsili 1:95

Ishaq ibn Isma'il narrated to us, Jarir and Abu Mu'awiyah narrated to us, from al-A'mash, from Abu Salih, who said: Abu Bakr al-Siddiq said: The Messenger of Allah (may Allah bless him and grant him peace) stood in a position like my position, then he wept and said: "Ask Allah for well-being (al-'afiyah), for no one has been given anything better than well-being, except for certainty (al-yaqin)." And Abu Mu'awiyah said: "Except for certainty."