The Book of Faith (Kitab Al-Iman)
Muslim :: Book 1 : Hadith 424
Abu Hazim narrated it on the authority of Ibn Sa'd that the Messenger of Allah (may peace be upon him) said: Seventy thousand persons or seven hundred thousand persons (Abu Hazim does not remember the exact number) would enter Paradise holding and supporting one another, and the first among them would not enter till the last among them would enter (therein) ; (they would enter simultaneously) and their faces would be bright like the full moon.