Allah's Messenger (ﷺ) said, "When the month of Ramadan starts, the gates of the heaven are opened and the gates of Hell are closed and the devils are chained."
Sahih al-Bukhari Book 30, Hadith 9
← Previous Hadith Allah's Messenger (ﷺ) said, "When Ramadan begins, the gates of Paradise are opened."

Sahih al-Bukhari Book 30, Hadith 8 Next 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