Let darkness seize upon it, i. e. constant and extraordinary darkness, without the least glimmering of light from the moon or stars. Joined unto the days of the year, i.e. reckoned as one, or a part of one, of them. The night is distinguished from the artificial day, but it is a part of the natural day, which consists of twenty-four hours. Or rather, let it not rejoice among the days, &c. Joy here, and terror, Job 3:5, are poetically and figuratively ascribed to the day or night with respect to men, who either rejoice or are affrighted in it. Let it be a sad, and as it were a funeral, day. Let it not come into the number of the months, i.e. to be one of those nights which go to the making up of the months.
Related Commentaries of Job 3:6
Job 3:6
6 As for that night, let darkness seize upon it; let it not be joined unto the days of the year, let it not come into the number of the months.