Albert Barnes Commentary Job 18:6

"The light shall be dark in his tent, And his lamp above him shall be put out." — Job 18:6 (ASV)

And his candle - The marginal note indicates 'lamp.' The reference is to a lamp that was suspended from the ceiling. The Arabians are fond of this image. Thus, they say, “Bad fortune has extinguished my lamp.” Of a man whose hopes are utterly destroyed, they say, “He is like a lamp which is immediately extinguished if you let it sink in the oil.” (See Schultens).

The putting out of a lamp is, for people in Eastern cultures, an image of utter desolation. It is the universal custom to keep a light burning in their houses at night. “The houses of Egypt, in modern times, are never without lights; they burn lamps all the night long, and in every occupied apartment.

So essential is this custom considered for a family's comfort, and so compelling is the power it exercises, that the poorest people would rather reduce their food supply than neglect it.” (Paxton). It is probable that this custom prevailed in former times in Arabia, just as it does now in Egypt; and this understanding will give increased beauty and force to this passage.