Job 41:23

The verse reads,

The flakes of his flesh cleave fast together;

It is firm upon him, it is not moved.

The "flakes" of his flesh are the parts beneath the neck and belly, which in most animals are soft and pendulous; in him they are firm and hard. In the second clause itrefers to his flesh, which is "firm," lit. castor molten, and does not move, or shake, with the motions of his body.