Riyad as-SalihinChapter 8Hadith 509
Full Sharh — Riyad as-Salihin 509
وعنه، رضي الله عنه قال: كان رسول الله صلى الله عليه وسلم، يرغب في قيام رمضان من غير أن يأمرهم فيه بعزيمة، فيقول: "من قام رمضان إيمانًا واحتسابًا غفر له ما تقدم من ذنبه" . ((رواه مسلم)).
English Translation
Abu Hurairah (May Allah be pleased with him) reported:: The Messenger of Allah (ﷺ) used to urge (the people) to perform (optional Tarawih) prayer at night during the month of Ramadan. He did not order them or make it obligatory on them. He (ﷺ) said, "Whosoever performs (optional Tarawih) prayers at night during the month of Ramadan, with Faith and in the hope of receiving Allah's reward, will have his past sins forgiven.".
Source
Riyad as-Salihin(رياض الصالحين)
The Book of Virtues
Hadith Number
509