Jamieson, Fausset and Brown on Job 16:15

15. sewed--denoting the tight fit of the mourning garment; it was a sack with armholes closely sewed to the body.

horn--image from horned cattle, which when excited tear the earth with their horns. The horn was the emblem of power (1Ki 22:11). Here, it is

in the dust--which as applied to Job denotes his humiliation from former greatness. To throw one's self in the dust was a sign of mourning; this idea is here joined with that of excited despair, depicted by the fury of a horned beast. The Druses of Lebanon still wear horns as an ornament.