Sayyiduna Sahl bin Sa'd (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "Indeed, in Paradise there is a gate called al-Rayyan; only those who fast will enter through it on the Day of Resurrection, and no one else will enter with them. It will be said: Where are those who fasted? So let them enter through it. When the last of them has entered, it will be closed, and no one will enter after them."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8511