The recommendation to pray at night in Ramadan - that is the tarawih prayers

Riyad as-Salihin (The Meadows of the Righteous)

by Imam Nawawi

213. Chapter: The recommendation to pray at night in Ramadan - that is the tarawih prayers

1187. Abu Hurayra reported that the Messenger of Allah, may Allah bless him and grant him peace, said, "Anyone who prays in Ramadan motivated by belief and in expectation of the reward will be forgiven his past wrong actions." [Agreed upon]

1188. Abu Hurayra said, "The Messenger of Allah, may Allah bless him and grant him peace, used to encourage prayer at night in Ramadan although he did not command people to do it as a obligatory duty. He would say, 'Anyone who prays in Ramadan motivated by belief and in expectation of the reward will be forgiven all his past wrong actions.'" [Muslim]