It is narrated from Sayyiduna Sahl bin Sa'd (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Paradise has a gate called al-Rayyan. On the Day of Resurrection it will be said: Where are those who fast? When they have all entered, it will be closed, and no one other than them will enter through it."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5743