Abu Hurayrah (may Allah be pleased with him) said: I heard the Prophet (peace and blessings be upon him) say: "Whoever stands (in prayer) in Ramadan with faith and seeking reward, his past sins will be forgiven."
(b) It is narrated from Abu Salamah (may Allah have mercy on him) that he (peace and blessings be upon him) said: "Whoever fasts Ramadan," and said: "Whoever stands (in prayer) on Laylat al-Qadr."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4598