Musnad Abu Ya'la al-Mawsili 1:84

Ishaq ibn Isma'il al-Taliqani narrated to us, Yahya ibn Abi Bukayr narrated to us, Zuhayr ibn Muhammad narrated to us, from Abdullah ibn Muhammad ibn Aqil, from Mu'adh ibn Rifa'ah ibn Rafi' al-Ansari, from his father Rifa'ah, who said: I heard Abu Bakr al-Siddiq saying upon the pulpit: I heard the Messenger of Allah, may Allah bless him and grant him peace—and Abu Bakr wept when he mentioned the Messenger of Allah, may Allah bless him and grant him peace, then he was relieved, then he said: I heard the Messenger of Allah, may Allah bless him and grant him peace—and Abu Bakr wept when he mentioned the Messenger of Allah, may Allah bless him and grant him peace, then he was relieved, then he said: I heard the Messenger of Allah, may Allah bless him and grant him peace, during this summer heat last year, saying: "Ask Allah for pardon, well-being, and certainty in the Hereafter and the first [life]."