Musnad Ahmad 1:43

'Abd al-Rahman ibn Mahdi narrated to us, Mu'awiyah—meaning Ibn Salih—narrated to us, from Sulaym ibn 'Amir al-Kala'i, from Awsat ibn 'Amr, who said: I arrived in Medina one year after the death of the Messenger of Allah, may Allah bless him and grant him peace, and I found Abu Bakr addressing the people. He said: "The Messenger of Allah, may Allah bless him and grant him peace, stood among us last year," and he was choked by tears three times. Then he said: "O people, ask Allah for well-being (al-mu'afah), for no one has been given anything better than certainty after well-being, nor anything more severe than doubt after disbelief. And you must be truthful, for it leads to righteousness, and both of them are in Paradise. And beware of lying, for it leads to wickedness, and both of them are in the Fire."