His roots shall be dried up beneath, and above shall his branch be cut off.
Roots - himself.
Branch - his children (Job 8:12; Job 15:30; Malachi 4:1, "The day that cometh shall burn them up, that it shall leave them neither root nor branch.").
Related Commentaries of Job 18:16
Job 18:16
16 His roots shall be dried up beneath, and above shall his branch be cut off.