Musnad Abu Ya'la al-Mawsili 252:20

Yahya ibn Ayyub narrated to us, Sa'id ibn 'Abd al-Rahman narrated to us, from Abu Hazim, from Sahl ibn Sa'd, that the Messenger of Allah (peace be upon him) said: "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 will never thirst again."