Musannaf Ibn Abi Shayba 33:461

Muhammad ibn Bishr al-‘Abdi narrated to us, from ‘Amr ibn Maymun, from his father, from a man from Banu Sulaym who is called ‘Abdullah ibn Saydan, he said: I accompanied Abu Dharr, and he said to me: Shall I not tell you about the day of my need? Indeed, the day of my need is the day I am placed in my grave; that is the day of my need.