Yahya related to me from Malik from Ibn Shihab from Abu Salamaibn Abd ar-Rahman ibn Awf from Abu Hurayra that the Messenger ofAllah, may Allah bless him and grant him peace, used to exhort peopleto watch the night in prayer in Ramadan but never ordered itdefinitely. He used to say, "Whoever watches the night in prayer inRamadan with trust and expectancy, will be forgiven all his previouswrong actions."Ibn Shihab said, "The Messenger of Allah, mayAllah bless him and grant him peace, died while that was still thecustom, and it continued to be the custom in the caliphate of Abu Bakrand at the beginning of the caliphate of Umar ibn al-Khattab."
App reference: Book 6, Hadith 2
USC-MSA web (English) reference: Book 6, Hadith 2
Arabic reference: Book 6, Hadith 248