C. F. Keil and Franz Delitzsch on Esther 4:1

Est 4:1

Mordochai learnt all that was done, - not only what had been openly proclaimed, but, as is shown by Est 4:7, also the transaction between the king and Haman. Then he rent his garments, put on sackcloth and ashes, and went out into the midst of the city, making loud and bitter lamentation. Comp. on the last words, Gen 27:34. The combination of אפר with שׂק ילבּשׁ is an abbreviation for: put on a hairy garment and spread ashes upon his head, in sign of deep grief; comp. Dan 9:3; Job 2:12, and elsewhere.