We used to prepare for the Messenger of Allah (may Allah's peace and blessings be upon him) his tooth-stick and the water he used for making ablution. Then, Allah would awaken him whenever He willed during the night, and he would brush his teeth with the tooth-stick, make ablution, and perform prayer

‘Ā'ishah (may Allah be pleased with her) tells that she used to prepare for the Messenger of Allah (may Allah's peace and blessings be upon him) his tooth-stick and the water with which he would make ablution at night. Then Allah, Blessed and Exalted, would wake him from his sleep at any time of the night. When he woke up, he would begin with cleaning his teeth with the tooth-stick in order to remove the odor that affects the mouth because of sleep.

Then he would make ablution for prayer, then offer voluntary night prayer.