sack·cloth 
/ˈsækˌklɑ:θ/ noun
/ˈsækˌklɑ:θ/ noun [noncount] : rough cloth that is used for making sacks
sackcloth and ashes
◊To don/wear sackcloth and ashes means to publicly express or show sorrow or regret for having done something wrong.
▪ He should be forced to wear sackcloth and ashes and apologize for his lies.
▪ He should be forced to wear sackcloth and ashes and apologize for his lies.
