In the name of Allah, Most Gracious, Most Merciful.
Sahl bin Sa’d (May Allah be pleased with him): The Prophet (May Allah exalt his mention and protect him from imperfection) said: “In Jannah there is a gate which is called “Ar-Rayaan” through which only those who observe Saum (fasting) will enter on the Day of Resurrection. None else will enter through it. It will be called out, “Where are those who observe fasting?” So they will stand up and proceed towards it. When the last of them will have entered, the gate will be closed and then no one will enter through that gate.” (Muslim)
Riyaadiss-Saliheen (The Meadows of the Righteous)
By Imam An Nawawi
Chapiter 217, Page 355, No 1217