Musannaf Ibn Abi Shayba 33:362

Zayd ibn al-Hubab narrated to us, from Mu'awiyah ibn Salih, from 'Abd al-Rahman ibn Jubayr ibn Nufayr, from his father, from Abu al-Darda', who said: "Indeed, those whose tongues remain moist with the remembrance of Allah will enter Paradise while they are laughing."