Matthew Poole and continuators on Jonah 3:6

6 For word came to the king of Nineveh, and he arose from his throne , and he laid his robe from him , and covered him with sackcloth , and sat in ashes .

This now accounteth for the peoples proclaiming a fast ver. 5. they did it because 'twas commanded, and they had the Kings example herein.

Whether Ionah did particularly speak to his hearers to send word to the King or whether the strangeness of the thing might move some or other to report it to the Courtiers, and they to the King is not specified, certain 'tis that the King had word brought him, and it was considered by him, nor is it said who this King was, Sardanapalus seems too early, Phul Belochus is with more probability thought to be this King.

Came down from his Royal seat.

Put off his rich, gorgeous and luxurious apparel.

Put on the rough, and uneasie garments of a mourner.

As Iob 2.8. and 42.6. Esth. 4.13.