Sayyiduna Abu Hurayrah (may Allah be pleased with him) says that the Messenger of Allah (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." Al-Bukhari (may Allah have mercy on him) said: And the Prophet (peace and blessings be upon him) said: "Whoever fasts Ramadan", and he also said: "Do not precede Ramadan (by fasting before it)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 7906