Musannaf Ibn Abi Shayba 33:333

Abdullah ibn Idris narrated to us, from his father, from al-Minhal ibn Amr, from Qays ibn Sakan, from Abdullah regarding His saying: "Their light will run before them," he said: They are given their light according to the measure of their deeds. Among them is he whose light is like the mountain, and among them is he whose light is like the palm tree. And the lowest of them in light is he whose light is upon his thumb; it is extinguished at one time and ignited at another.