Musnad Abu Ya'la al-Mawsili 151:81

Abdullah ibn Awn al-Khazzaz narrated to us, Marwan ibn Mu'awiyah narrated to us, from Aban ibn Ishaq, from al-Sabah ibn Muhammad ibn Abi Hazim, from Murrah al-Hamdani, from Abdullah ibn Mas'ud, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Be shy of Allah with true shyness. Let the head be guarded and what it contains, and let the stomach be guarded and what it gathers. Let one remember death and decay. Whoever desires the Hereafter leaves the adornment of the worldly life. Whoever does that has been shy of Allah with true shyness."