Whoever fasts Ramadhan with faith and hoping for reward, he will be forgiven for all of his previous sins. Whoever stands (for prayer at night) during Ramadhan with faith and hoping for reward, he will be forgiven for all of his previous sins. Whoever stands (for prayer at night) during Laylatul-Qadr (the Night of Decree) with faith and hoping for reward, he will be forgiven for all of his previous sins. [Al-Bukhari no.2014 and Muslim no. 759-760]