Jonah 3:5

So, Heb. And, the people of Nineveh; the inhabitants who heard; they first believed who first heard, and successively others as soon as they heard. Believed God, speaking by his prophet; they knew their own sins. Though Jonah were a stranger to them, yet because, coming in God's name, he did very particularly, fully, and to the life enumerate, decipher, and lay open their sins, with what they deserved, what might be expected, what God threatened from heaven, all which concurring wrought them to believe their danger, God's mercy, and the possibility of escape if they repent. Whether the fame of Jonah's deliverance came to Nineveh before him appears not, nor is it likely it should come so far and so fast, though it were known on the Syrian coast, and about Tyre and Zidon; possibly Jonah might publish it in Nineveh. Proclaimed a fast; every one called upon other to fast, of cried out it was high time to fast, repent, and supplicate God, so some think; but this passage is an anticipation, tells us what was done, and will tell us afterwards on what grounds, authority, and example it was done. Put on sackcloth; a ceremony very usual in mournings, private or public, in those countries, and a token of their true mourning; this all did, great and small, rich and poor.