Sunan Ibn Majah, Chapter: The Chapters of Establishing the Prayer and the Sunnah Regarding Them

"I asked Aishah: 'With what did the Prophet (saw) start his voluntary prayers?' She said: 'He would say: "Allahumma Rabba Jibra'il wa Mika'il wa Israfil, Fatiras-samawati wal-ard, 'alimal-ghaybi wash- shahadah, Anta tahkumu baina 'ibadika fima kanu fihi yakhtalifun, ahdini lima akhtulifa fihi minal-haqqi bi ihdnika, innaka latahdi ila siratin mustaqim (O Allah, Lord of Jibra'il, Mika'il and Israfil, Creator of the heavens and the earth, Knower of the unseen and the seen, You judge between Your slaves concerning that wherein they differ. Guide me to the disputed matters of truth by Your Leave, for You are the One Who guides to the straight Path)." Hasan