سنن النسائي

An-Nadr bin Shaiban said: "I said to Abu Salamah bin 'Abdur-Rahman: 'Tell me of something that you heard from your father, that he heard from the Messenger of Allah, with no one in between your father and Messenge of Allah concerning the month of Ramadan. He said: 'Yes; my father said: The Messenger of Allah (ﷺ) said: Allah, may He be blessed and exalted, enjoined the fast of Ramadan upon you, and I have made it Sunnah for you to spend its nights in prayer. Whoever fasts it and spends its nights in prayer out of faith and in the hope of reward, he will emerge from his sins as on the day his mother bore him."' (Daif)