The Prophet (ﷺ) said, "Whoever established prayers on the night of Qadr out of sincere faith and hoping for a reward from Allah, then all his previous sins will be forgiven; and whoever fasts in the month of Ramadan out of sincere faith, and hoping for a reward from Allah, then all his previous sins will be forgiven."
Sahih al-Bukhari Book 30, Hadith 11
← Previous Hadith I heard Allah's Messenger (ﷺ) saying, "When you see the crescent (of the month of Ramadan), start fasting, and when you see the crescent (of the month of Shawwal), stop fasting; and if the sky is overcast (and you can't see it) then regard the month of Ramadan as of 30 days."

Sahih al-Bukhari Book 30, Hadith 10 Next Hadith → The Prophet (ﷺ) was the most generous amongst the people, and he used to be more so in the month of Ramadan when Gabriel visited him, and Gabriel used to meet him on every night of Ramadan till the end of the month. The Prophet (ﷺ) used to recite the Holy Qur'an to Gabriel, and when Gabriel met him, he used to be more generous than a fast wind (which causes rain and welfare).

Sahih al-Bukhari Book 30, Hadith 12