Narrated Abu Huraira:

(May Allah be pleased with him)

“I heard Allah’s Apostle
(peace and blessings of Allaah be upon him)
saying regarding Ramadan, “
Whoever prayed at night in it (the month of Ramadan) out of sincere Faith
and hoping for a reward from Allah, then all his previous sins will be forgiven.”
{ Al-Bukhari & Muslim }