Genesis 37:34

Jacob rent his clothes.

Rending the clothes was an expression of the deepest feeling, whether of sorrow or indignation. Reuben rent his clothes when he returned and found the pit empty in which Joseph had been cast. The high priest rent his clothes when Jesus declared before the Sanhedrim that he was the Son of God. When Abner was slain King, David commanded Joab the murderer, "and all the people with him, Rend your clothes, and gird you with sackcloth, and mourn before Abner."

Put sackcloth upon his loins.

Sackcloth was the usual garb of mourning, as in our times crape is worn.