Sahih Muslim Book 4, Hadith Number 1701.

Chapter : Preference for prolonging recitation in the night prayer.

Husain b. ‘Ali narrated on the authority of (his father) ‘Ali b. Abu Talib that the Apostle of Allah (may peace be upon him) came one night to see him (‘Ali) and Fatimah (the daughter of the Holy Prophet) and said: Don’t you observe (Tahajjud) prayer? I (‘Ali) said: Messenger of Allah, verily our souls are in the hands of Allah and when He wants to awaken us, He awakens us. The Messenger of Allah (may peace be upon him) went back when I said this to him. He was striking his hand on his thigh while returning, and I heard him say: Verily the man disputes with many things.