Sackcloth and Ashes
Although the modern-day idea of "wearing sackcloth" is often that of someone dressed in a burlap grain bag with head and arm holes cut in it, during Bible History its appearance was quite different. Sackcloth was most often made of coarse, black goat's hair. As its name indicates, it was used for sacks, but was also customarily worn by mourners (in some countries, the ancient custom is still faintly seen today when mourners wear black arm bands at funerals), or as a sign of deep repentance and humility. Ashes were often included as a further symbol of personal abhorrence and chagrin. Also, sackcloth was, and will be (in some contemporary form), in the case of the two witnesses, worn by some Prophets.
"Then Jacob rent his garments, and put sackcloth upon his loins, and mourned for his son many days." (Genesis 37:34 RSV) (see Coat Of Many Colors)
"Then David said to Joab and to all the people who were with him, "Rend your clothes, and gird on sackcloth, and mourn before Abner." And King David followed the bier." (2 Samuel 3:31 RSV)
"When Mordecai learned all that had been done, Mordecai rent his clothes and put on sackcloth and ashes, and went out into the midst of the city, wailing with a loud and bitter cry" (Esther 4:1 RSV) (see Haman)
"Then He began to upbraid the cities where most of His mighty works had been done, because they did not repent. "Woe to you, Chorazin! woe to you, Bethsaida! for if the mighty works done in you had been done in Tyre and Sidon, they would have repented long ago in sackcloth and ashes." (Matthew 11:20-21 RSV) (see Miracles Of Jesus Christ)
"So Jonah arose and went to Nineveh, according to the word of The Lord. Now Nineveh was an exceedingly great city, three days' journey in breadth. Jonah began to go into the city, going a day's journey. And he cried, "Yet forty days, and Nineveh shall be overthrown!" And the people of Nineveh believed God; they proclaimed a fast, and put on sackcloth, from the greatest of them to the least of them. Then tidings reached the king of Nineveh, and he arose from his throne, removed his robe, and covered himself with sackcloth, and sat in ashes. And he made proclamation and published through Nineveh, "By the decree of the king and his nobles: Let neither man nor beast, herd nor flock, taste anything; let them not feed, or drink water, but let man and beast be covered with sackcloth, and let them cry mightily to God; yea, let every one turn from his evil way and from the violence which is in his hands." (Jonah 3:3-8 RSV)
"And I will grant My two witnesses power to prophesy for one thousand two hundred and sixty days, clothed in sackcloth." These are the two olive trees and the two lampstands which stand before the Lord of the earth. And if any one would harm them, fire pours out from their mouth and consumes their foes; if any one would harm them, thus he is doomed to be killed. They have power to shut the sky, that no rain may fall during the days of their prophesying, and they have power over the waters to turn them into blood, and to smite the earth with every plague, as often as they desire." (Revelation 11:3-6 RSV) (see The Two Witnesses and Are The Two Witnesses Here Now?)
Fact Finder: During the great events prior to The Return Of Jesus Christ, will the "sun become black as sackcloth"?
See also Signs In The Heavens