Musannaf Ibn Abi Shayba 21:333

Zayd ibn al-Hubab narrated to us, Mu'awiyah ibn Salih informed us, he said: 'Amr ibn Qays al-Kindi informed me, from 'Abdullah ibn Busr, that a Bedouin said to the Messenger of Allah (may Allah bless him and grant him peace): "O Messenger of Allah, the laws of Islam have become too many for me, so inform me of a matter that I may hold fast to." He said: "Let your tongue remain moist with the remembrance of Allah."