strength. parts or members of his body.
skin. Put by Figure of speech Synecdoche (of the Part), App-6, for the whole body. Compare Exodus 22:26.
firstborn of death: i.e. the chief, or worst, or cruellest death. Figure of speech Euphemismos. App-6.
Related Commentaries of Job 18:13
Job 18:13
13 It shall devour the strengthe of his skin: even the firstborn of death shall devour his strength.