“I asked ‘Aishah: ‘With
what did the Prophet (ﷺ) start voluntary prayers?’ She said: ‘You
have asked me about something which no one has asked before. He used
to say Allahu Akbar ten times, and Al-Hamdu Lillah ten times and
Subhan Allah ten times, and he would say Allahumma aghfirli wahdini,
warzuqni, wa ‘afini (O Allah, forgive me, guide me, grant me
provision
and give me good health),” and he would seek refuge from
the
difficulty of the standing on the Day of Resurrection.”
Sunan Ibn Majah Book 5, Hadith 554