Hadith: When Ramadan comes, the gates of Paradise are opened, the gates of Hell are closed, and the devils are chained

عن أبي هريرة رضي الله عنه : أن رسول الله صلى الله عليه وسلم قال: «إِذَا جَاءَ رَمَضَانُ، فُتِحَتْ أبْوَاب الجَنَّةِ، وَغُلِّقَتْ أبْوَابُ النَّارِ، وَصفِّدَتِ الشَّيَاطِينُ».
[صحيح] - [متفق عليه]

Abu Hurayrah (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said: "When Ramadan comes, the gates of Paradise are opened, the gates of Hell are closed, and the devils are chained."
Sahih/Authentic. - [Al-Bukhari and Muslim]

Explanation

Abu Hurayrah reported that the Prophet (may Allah's peace and blessings be upon him) said that when the month of Ramadan begins, the gates of Paradise are opened, the gates of Hell are closed, and the devils are chained. These are three things that happen during Ramadan: First: the doors of Paradise are opened, as an encouragement for those working to enter Paradise by performing more good deeds such as prayer, charity, remembering Allah, reciting the Qur'an, etc. Second: the doors of the Hellfire are closed, due to the less amount of sins committed by the believers in Ramadan. Third: the devils are chained up, meaning the strongest devils, or the "Maradah" as stated in another narration. This version was narrated by Imām An-Nasāi in his Sunan (4/434, no. 2105), and Imām Ahmad in his Musnad (2/292). Al-Albāni said: "It is a good Hadīth by virtue of supporting evidence." [Mishkat al-Masabīh 1/612, no. 1962] The "Maradah" are the strongest devils who are the most hostile towards humans. They are chained up, meaning that their hands are tied so that they are prevented from causing harm that they could do in other than Ramadan. This and everything else that the Prophet (may Allah's peace and blessings be upon him) said is the truth, and he informed us of it to give advice to Muslims, encourage them to do good and warn them from evil.