Musnad Ahmad 1013:45

Sulayman ibn Dawud al-Hashimi and Ishaq ibn Isa narrated to us, they said: Sa'id ibn Abd al-Rahman narrated to us, from Abu Hazim, from Sahl ibn Sa'd, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, for the fasting people there is a gate in Paradise called al-Rayyan; no one enters through it except them. When the last of them has entered, it will be closed. Whoever enters through it will drink, and whoever drinks from it will never thirst again."