The people of Nineveh believed God - They had no doubt that the threatening would be fulfilled, unless their speedy conversion prevented it; but, though not expressed, they knew that the threatening was conditional. "The promises and threatenings of God, which are merely personal, either to any particular man or number of men, are always conditional, because the wisdom of God hath thought fit to make these depend on the behavior of men." - Dr. S. Clarke's Sermons, vol. i.
Proclaimed a fast - And never was there one so general, so deep, and so effectual. Men and women, old and young, high and low, and even the cattle themselves, all kept such a fast as the total abstinence from food implies.

So the people of Nineveh believed God,.... Or "in God" (r): in the word of the Lord, as the Targum; they believed there was a God, and that he, in whose name Jonah came, was the true God; they believed the word the prophet spake was not the word of man, but, the word of God; faith came by hearing the word, which is the spring of true repentance, and the root of all good works. Kimchi and R. Jeshuah, in Aben Ezra, suppose that the men of the ship, in which Jonah had been, were at Nineveh; and these testified that they had cast him into the sea, and declared the whole affair concerning him; and this served greatly to engage their attention to him, and believe what he said: but this is not certain; and, besides, their faith was the effect of the divine power that went along with the preaching of Jonah, and not owing to the persuasion of men;

and proclaimed a fast; not of themselves, but by the order of their king, as follows; though Kimchi thinks this was before that:

and put on sackcloth, from the greatest of them even to the least of them; both, with respect to rank and age, so universal were their fasting and mourning; in token of which they stripped themselves of their common and rich apparel, and clothed themselves with sackcloth; as was usual in extraordinary cases of mourning, not only with the Jews, but other nations.

(Jonah would be a quite a sight to behold. The digestive juices of the fish would have turned his skin to a most unnatural colour and his hair was most like all gone. Indeed, anyone looking like that would attract your attention and give his message more credence, especially after he told you what had happened to him. A God who creates storms, prepares large fish to swallow a man and preserves him in the fish, would not likely have too much trouble destroying your city. Editor)

(r) "in Deum", V. L.

believed God--gave credit to Jonah's message from God; thus recognizing Jehovah as the true God.

fast . . . sackcloth--In the East outward actions are often used as symbolical expressions of inward feelings. So fasting and clothing in sackcloth were customary in humiliation. Compare in Ahab's case, parallel to that of Nineveh, both receiving a respite on penitence (; ; ).

from the greatest . . . to the least--The penitence was not partial, but pervading all classes.