Sackcloth was Worn by God's Prophets
Source: TTT
2 Kings 1:8
“He was a hairy man,” they answered, “with a leather belt around his waist.” “It was Elijah the Tishbite,” said the king.
Isaiah 20:2
the LORD had already spoken through Isaiah son of Amoz, saying, “Go, remove the sackcloth from your waist and the sandals from your feet.” And Isaiah did so, walking around naked and barefoot.
Matthew 3:4
John wore a garment of camel’s hair, with a leather belt around his waist. His food was locusts and wild honey.
Revelation 11:3
And I will empower my two witnesses, and they will prophesy for 1,260 days, clothed in sackcloth.”