In the third chapter of the Book of Jonah, Jonah finally reaches Nineveh, and starts preaching repentance and reformation to the people there. And... they listen! Even the King of Assyria listens!

The inner meaning of the story is pretty close to the surface here, and there's important symbolism. Swedenborg summarizes the chapter's meaning in this one sentence:

"The nations, hearing from the Word of God about their sins, and that they would perish, were converted after repenting, and were heard by the Lord, and saved." (The Inner Meaning of the Prophets and Psalms 213)

Rev. George McCurdy, in his exegesis of this chapter, offers this summary:

The great city of Nineveh has many spiritual representations. The world saw Nineveh as a mighty nation, but in the eyes of the Lord, it represented the shallowness and weakness (death) of false doctrines, contrived beliefs confirmed by the proprium (self love), the fallacies of the senses, and the unenlightened understanding that spawns spiritual ignorance.

The Lord’s mercy and love for all prompted Him not only to send His message to Nineveh, but to ensure that it would be preserved for eternity. Jonah’s call to "arise and go" preach to Nineveh is a call for spiritual renewal. It is a call for repentance. The fasting, sackcloth, and ashes symbolize a call to be aware that "where there is no truth, there is no church."

Where the Word is closed, and not loved, there is a loss of conjunction with the Divine resources. The fasting of man and beast symbolizes a need for the spiritual and natural appetites to come to the Lord for that "bread which comes down from heaven." The Ninevites giving up their natural food and drink represents their turning away from "as-of-self" concepts and reminds all who read and hear the Word of the Lord to rely on heavenly manna.

"Why do you spend money for what is not bread, and your wages for what does not satisfy? Listen carefully to Me and eat what is good, and let your soul delight itself in abundance…" (Isaiah 55:2)

The king sitting in ashes and mourning represents a sorrowful attitude toward "the remains of the fire of self-love." Repentance involves self-examination, making oneself guilty for the sins and evils committed, asking the Lord for His help, and desiring to attain a new life.

As we mull over this concept, think about the Lord’s preaching on earth. As He went about His mission, He often used these words: "You have heard it said of old… but I say unto you…" Putting aside human traditions and taking on the Lord’s teachings is an ongoing effort. Jonah was told to preach the words of the Lord. He was not to make things up from his memory. He was to be a true and faithful prophet of the Lord’s ways.

Here's a link to an interesting (audio) sermon on this chapter, by Rev. Todd Beiswenger.

Rev. Martin Pennington suggests two explanatory passages from Swedenborg's theological writings:

"Forty days means a period of temptation combats or severe change." (Arcana Coelestia 730)

"A fast represents those who are in a state of unhappiness when good is no longer joined to the truths." (Arcana Coelestia 9182[10])

Other references of interest listed by Rev. McCurdy include:

"As ‘forty’ signified what is full or complete… forty signifies what is complete in respect to instruction and influx… for this reason it was said by Jonah to the Ninevites that ‘the city would be overthrown after forty days" (Jonah 3:4) (Arcana Coelestia 9437[2])

"By being clothed in sackcloth is signified mourning on account of the vastated truth in the church; for garments signify truths; and therefore, to be clothed in sackcloth, which is not a garment, signifies mourning that there is no truth; and where there is no truth, there is no church." Jonah 3:5-6 is cited. (Apocalypse Revealed 492)

"…the rite of putting sackcloth on the loins to testify…mourning may be seen from the historic and prophetic parts of the Word, as in… Jonah 3:5-8… for a sign representative of mourning over the evil on account of which Nineveh was to perish; thus over destroyed good." (Arcana Coelestia 4779[2])

"From the signification of garments it is also manifest why they rent their garments, when any one spoke against the Divine truth of the Word… and why, on account of transgressions against Divine truths, they put off their garments, and put on sackcloth." Jonah 3:5, 6, and 8 are cited. (Apocalypse Revealed 166)

"That ‘ashes’ denote falsity, may be confirmed from passages where another word for ‘ashes (cinis)’ is used, for these ashes have a like origin…" Jonah 3:6 is cited. (Arcana Coelestia 7520)

"…by ‘ashes’ in the opposite sense, namely, what is condemned that remains after the burning from the fire of self love. This is signified by ‘the ashes’ which they carried on the head, and in which they rolled themselves when bewailing their sins." Jonah 3:6 is cited. (Arcana Coelestia 9723)

"In the spiritual sense by kings those who are in truths are signified, by the great ones those who are in goods, by the rich those that are in the knowledge of good, by the mighty they that are in erudition, by servants they that are in such things from others, and thus from memory, and by freemen they that are in such things from themselves…" Jonah 3:7 is cited. (Apocalypse Revealed 337)

"The interior good and also the interior evil…are signified by ‘man,’ are those which are of the intention or end, for the intention or end is the inmost of man; but the exterior good and also the exterior evil which are signified by ‘beast,’ are those which are of the thought, and of the consequent action when nothing stands in the way…By ‘beast,’…in respect to the external or natural man, a man is nothing else than a beast, for he takes delight in the like cupidities and pleasures, as also in the like appetites and sense…Therefore… from a holy rite it was commanded by the king of Nineveh, that both man and beast were to fast, and were to be covered with sackcloth (Jonah 3:7, 8)." (Arcana Coelestia 7523)

"… in the spiritual world a man’s affections appear at a distance like beasts… and beasts, viewed in themselves, are nothing but forms of natural affections… By man and beasts together is signified man as to spiritual and natural affection, in the following passages… Jonah 3:7, 8…" (Apocalypse Revealed 567)

"Here ‘webs’ and ‘garments’ are predicated of things of the understanding, that is, of the thought; ‘iniquity’ and ‘violence,’ of things of the will, that is, of works. In Jonah 3:8… the ‘evil way’ is predicated of falsities, which are of the understanding; and ‘violence,’ which are of the will." (Arcana Coelestia 623[2])

"…the ‘wrath of anger’ is attributed to Jehovah, and consequently ‘repentance.’" (Arcana Coelestia 588[2])

"…the Word is such in the sense of the letter, it may be evident that it cannot be understood without doctrine. But let examples illustrate this. It is said that Jehovah repenteth (Jonah 3:9; 4:2), and it is also said that Jehovah repenteth not (Num. 23:19…): without doctrine these statements do not agree." (Teachings Regarding the Sacred Scripture 51)

"In these passages (Jonah 3:9,10) Jehovah is said to have ‘repented,’ when yet it cannot be that He repents, because He knows all things before He does them; from which it is evident that by ‘repenting’ is signified mercy." (Arcana Coelestia 10441[2-4])

Finally, here's a link to Rev. McCurdy's study guide for the Book of Jonah, which is available for free as a .pdf, for your use.

9224. 'The firstborn of your sons you shall give to Me' means also all the matters of faith that [are acquired] through them - that they are to be ascribed to the Lord and not to self. This is clear from the meaning of 'the firstborn of sons' as all matters of faith the Church possesses, dealt with in 2435, 6344, 7035, 7039, 7778, 8042; and from the meaning of 'giving to Me' as ascribing to the Lord, 'Jehovah' being used in the Word to mean the Lord. All matters of faith, meant by 'the firstborn of sons', are beliefs which spring from the good of charity; for faith comes into being from this good. Whether truths are acquired from the Word or from the teachings of the Church, they cannot by any means become matters of faith without the presence of good in which they can be implanted. The reason for this is that the understanding part of the mind is that which receives truths first, for it sees them and introduces them into the will; and when those truths are in the will they are in the person, the will being the person's true self. Anyone therefore who supposes that faith is faith with a person before the person wills it, and does it because he wills it, is very much mistaken. Nor before this do the truths of faith themselves have life in them. All that which belongs to the will is called good, because it is loved; thus truth becomes good, or faith becomes charity, when it is in the will.

[2] There are two controversies which have bothered the Church since earliest times. The first is whether faith is the firstborn of the Church or whether charity is; and the second is whether faith separated from charity brings salvation. The reason why these two controversies arose was that before a person has been regenerated he discerns the truths that are to become matters of faith but not the good that is the good of charity. For the truths of faith enter by the external route, that is to say, through hearing; they deposit themselves in the memory, and from there they appear in the understanding. But the good of charity flows in by the internal route - through the internal man from heaven, that is, from the Lord by way of heaven. Therefore it does not come to be discerned until the truths called matters of faith start to be loved for the sake of performing good and useful service and leading a good life, which happens when they come to belong to the will. This now explains why faith was declared to be the firstborn of the Church, and also why people attributed to it the rights of the firstborn, that is, the rights of priority and superiority over the good of charity, when in actual fact the good of charity is prior and higher, and the truth of faith only apparently so, see 3325, 3494, 3539, 3548, 3556, 3563, 3570, 3576, 3603, 3701, 4925, 4926, 4928, 4930, 4977, 5351, 6256, 6269, 6272, 6273.

[3] The reason why those who belong to the Church have been in the dark in regard to these matters is that they have failed to perceive that all things in the universe have connection with truth and good, and to be anything must have connection with both. They have also failed to perceive that in the human being there are two mental powers, the understanding and the will, and that truth has connection with the understanding and good with the will, and that without the connection with both nothing is made a person's own. Because these considerations have lain in the dark, and yet the ideas composing a person's thought are based on such considerations, the error could not be made plain to the natural man. Yet if it had at some time been made plain, members of the Church would have seen from the Word as in broad daylight that the Lord Himself had countless things to say about the good of charity, that this good ranks first in the Church, and that faith does not exist anywhere else than within that good. The good of charity consists in doing good because one wills it. They would also have seen the errors that teachings upholding faith separated from charity bring in with them. One such error is the idea that a person is able to will evil and believe truth, consequently that truth is in agreement with evil. Another is the idea that faith can cause the life of heaven to exist with a person who has the life of hell in him, therefore that one life can be transformed into the other, so that those in hell can be raised to heaven and lead among angels a life contrary to their former life. People entertaining such errors do not take into consideration the fact that if anyone leads a life contrary to the life already acquired in the world he is deprived of his life. Anyone who tries to do so is like those who are in the throes of death and end their life in dreadful torment. Errors like these and very many others are what the teachings upholding faith separated from charity bring in with them.