The Messenger of Allah ﷺ said, "When the month of Ramadan enters, the gates of Paradise are opened, the gates of Hell are shut, and the devils are chained."
أخبرنا علي بن حجر قال حدثنا إسمعيل قال حدثنا أبو سهيل عن أبيه
أن رسول الله ﷺ قال إذا دخل شهر رمضان فتحت أبواب الجنة وغلقت أبواب النار وصفدت الشياطين
Reported by Muslim, Fasting, chapter on the merit of the month of Ramadan, no. 1079, from Ali bin Hajar, and by Bukhari, Fasting, chapter on whether one may say "Ramadan" or "the month of Ramadan," and on those who considered all such usage permissible, no. 1898, from the hadith of Ismail bin Jafar, through the same route. It is also found in Kubra, no. 2407.Abu Suhayl is Nafi bin Malik bin Abu Amir Al-Asbahi.