Sahih Muslim Book 6, Hadith Number 2643.

Chapter : One should exert more (in devotion and prayer) in the last ten days of Ramadhan.

‘Aisha (Allah be pleased with her) reported that when the last ten nights began Allah’s Messenger (may peace be upon him) kept awake at night (for prayer and devotion), wakened his family, and prepared himself to observe prayer (with more vigour).