Adam Clarke on Job 7:2

Earnestly desireth the shadow - As a man who labors hard in the heat of the day earnestly desires to get under a shade, or wishes for the long evening shadows, that he may rest from his labor, get his day's wages, retire to his food, and then go to rest. Night is probably what is meant by the shadow; as in Virgil, Aen. iv., ver. 7:

Humentemque Aurora polo dimoverat Umbram. "The morning had removed the humid shadow, i.e., night, from the world."

Where Servius justly observes:

Nihil interest, utrum Umbram an Noctem dicat: Nox enim Umbra terrae est, "It makes no difference whether he says shadow or night; for night is the shadow of the earth."