Narrated Aisha, Ummul Mu'minin:

Asim ibn Humayd said: I asked Aisha: By what words the Messenger of Allah (ﷺ) would begin his supererogatory prayer at night?

She replied: You ask me about a thing of which no one asked me before you. When he stood up, be uttered the takbir (Allah is most great) ten times, and uttered "Praise be to Allah" ten times, and uttered "Glory be to Allah " ten times, and uttered "There is no god but Allah" ten times, and sought forgiveness ten times, and said: O Allah, forgive me, and guide me, and give me sustenance, and keep me well, and he sought refuge in Allah from the hardship of standing before Allah on the Day of Judgment.

Abu Dawud said: This tradition has also been narrated by Khalid b. Ma'dan from Rab'iah al-Jarashi on the authority of 'Aishah.