To wear sackcloth and ashes means to show penitence, to show remorse, to be in mourning. The term sackcloth and ashes comes from the Bible, where someone in mourning would put on sackcloth made of a coarse material such as goat’s hair, and cover themselves in ashes. Such action showed that the person was enduring the most terrible disaster. In the Bible, sackcloth and ashes were also worn to show penitence and remorse in the hopes of appeasing the wrath of God. Today, the term sackcloth and ashes is used metaphorically to denote one’s guilt and willingness to do what is necessary to show one’s responsibility and penance for one’s wrongdoing.
Examples
From Baton Rouge to St. Paul and Dallas, and now France, the catalogue of violence and hate and wanton desecration of the sanctity of life resounds so loudly that the impulse is to cover oneself in sackcloth and ashes and sit mute on the ground in mourning. (The Huffngton POst)
When, on the other hand, the prophet Nathan confronted David, the king immediately confessed his sin and went into sackcloth and ashes as a mark of penitence. (The Liberian Daily Observer)
This too is not the Legislature’s role – to be a solicitous confessor dispensing sackcloth and ashes from the capital. (The Memphis Daily News)
Assuredly, the blasphemy of calling Curry the best will prompt some LeBron fans to rip off their clothes and put on sackcloth and ashes. (The San Jose Mercury News)
Fianna Fáil has obviously thrown off the sackcloth and ashes and is back wearing the flash pinstripes and the mohair suits. (The Irish Times)
“The Seagull,” 2010: A production from Falls’ mercifully brief phase wherein he eschewed the magnum opus, donned a metaphoric sackcloth and ashes and kept actors in the rehearsal room for weeks, this was still one of the deepest dives into the psyche of Anton Chekhov one ever is likely to see. (The Chicago Tribune)