“Let man and beast be covered with sackcloth”
Furthermore, let both man and beast be covered with sackcloth, and have everyone call out earnestly to God. (Jonah 3:8 BSB)
What it sounds like today
A bizarre, almost comic image of animals wearing sackcloth.
The cultural key
Draping the animals in sackcloth sounds absurd to modern ears, but it reflects a real ancient custom. In parts of the ancient Near East, extreme public mourning or repentance was expressed by the entire community, including its animals: flocks and herds were made to fast, kept from food and water, and even covered in sackcloth, so that the whole living population, human and animal, visibly shared the grief. It was a way of saying the calamity is total and our contrition is total. So when the king of Nineveh decrees that 'man and beast' put on sackcloth and cry out to God, he is ordering the most complete, all-encompassing act of repentance his culture knew, sparing nothing, involving everything that breathes. The detail underlines how thoroughly Nineveh turned. Read as comedy it is a talking-animals absurdity; read as custom it is a portrait of a city repenting with everything it had.
Recovered meaning
Putting animals in sackcloth and making them fast was a recognized way to express total, community-wide mourning and repentance; Nineveh's king marshals the whole city, people and livestock alike, into contrition. The odd detail shows how completely the city turned.