There was a wonder of Divine grace in the repentance and reformation of Nineveh. It condemns the men of the gospel generation, Mt 12:41. A very small degree of light may convince men that humbling themselves before God, confessing their sins with prayer, and turning from sin, are means of escaping wrath and obtaining mercy.
The people followed the example of the king. It became a national act, and it was necessary it should be so, when it was to prevent a national ruin. Let even the brute creatures' cries and moans for want of food remind their owners to cry to God.
In prayer we must cry mightily, with fixedness of thought, firmness of faith, and devout affections. It concerns us in prayer to stir up all that is within us. It is not enough to fast for sin, but we must fast from sin; and, in order to the success of our prayers, we must no more regard iniquity in our hearts, Ps 66:18.
The work of a fast-day is not done with the day. The Ninevites hoped that God would turn from his fierce anger; and that thus their ruin would be prevented. They could not be so confident of finding mercy upon their repentance, as we may be, who have the death and merits of Christ, to which we may trust for pardon upon repentance.
They dared not presume, but they did not despair. Hope of mercy is the great encouragement to repentance and reformation. Let us boldly cast ourselves down at the footstool of free grace, and God will look upon us with compassion.
God sees who turn from their evil ways, and who do not. Thus he spared Nineveh. We read of no sacrifices offered to God to make atonement for sin; but a broken and a contrite heart, such as the Ninevites then had, he will not despise.