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.

3701. 'And behold, the angels of God going up and coming down on it' means an infinite and eternal communication and the consequent joining together - a going up, so to speak, from what is lowest, and after that, when order has been inverted, a coming down to it. This is clear from the meaning of 'the angels' as some aspect of the Lord's Divine meant by the expression 'angels' when used in the Word, dealt with in 1925, 2319, 2821, 3039. The aspect meant here is Divine Truth. This is clear from the fact that they are called 'the angels of God', for the name God is used when truth is the subject in the internal sense, but Jehovah when good is the subject, see 2586, 2769, 2807, 2822. This is why although the name Jehovah is used directly after this in the phrase 'Jehovah standing above it', they are nevertheless referred to here as 'the angels of God', since the subject is truth from which good springs, represented by 'Jacob' here, as stated many times above. As regards the expression 'going up and coming down on the stairway' meaning in the highest sense infinite and eternal communication and the consequent joining together, this is clear without further explanation. But one cannot speak of a communication between, and the consequent joining together of the Lord's Divine itself and His Divine Human unless at the same time one calls these attributes infinite and eternal, for in the Lord everything is infinite and eternal - infinite so far as Being (Esse) is concerned and eternal so far as Manifestation (Existere) is concerned. From what has been stated up to now it is evident that 'a stairway set up on the earth, and its top reaching to heaven, and behold, the angels of God going up and coming down on it' means in a nutshell a going up so to speak from what is lowest, and after that, when order is inverted, a coming down to it.

[2] The nature of this going up and coming down becomes clear from what has been stated and shown above in 3539, 3548, 3556, 3563, 3570, 3576, 3603, 3607, 3610, 3665, 3690. But because this order - which comes into effect when a person is being regenerated and which is described in the internal sense here and in what follows - is completely unknown in the Church, let the nature of it be illustrated further: It is well known that a person is born into the same disposition as his parents, grandparents, and great grandparents, going back for centuries, and so into hereditary evil gradually accumulated by all those before him, so much so that there is nothing but evil in what he does when he acts from himself. As a consequence both his understanding and his will have been totally spoiled and of himself he does not will anything good at all and therefore does not understand anything true at all. That which he calls good, indeed believes to be good, is in fact evil, and that which he calls the truth, indeed believes to be the truth, is in fact falsity. Take, for example, loving himself more than others, wanting things to be better for himself than for others, desiring what belongs to someone else, and considering only himself and not others unless he himself will benefit. Because he desires these things of himself he indeed calls them good and also true. And what is more, if anyone harms or tries to harm these things which by him are called good and true, he hates him and is also filled with thoughts of revenge. He desires and also seeks that person's ruin, and takes delight in this insofar as he actually strengthens such intentions in himself, that is, as frequently as he actually puts them into effect.

[3] When such a person enters the next life his desires remain the same. The actual disposition which he has acquired in the world by the life he led remains, and that delight is perceived plainly by others. Consequently he is unable to be in any heavenly community where everyone wants things to be better for others than for himself; but he is in some community of hell whose delight is similar to his own. It is that disposition of his which needs to be rooted out while he is living in the world, something that cannot possibly be achieved except through regeneration from the Lord, that is, through receiving quite another will and therefore quite another understanding - by becoming a new person so far as both those powers of mind are concerned. But for this to come about he must first of all be born like a young child again, learn what evil and falsity are, and learn what good and truth are, for without knowledge or awareness of these he is unable to have any good conferred on him. Indeed of himself he does not acknowledge anything else as good except that which is evil, nor anything else as truth except that which is false.

[4] To make a person new, cognitions are instilled into him such as are not completely contrary to those he has already - for example, the idea that all love starts in himself; the idea that one should consider oneself first and others only after that; the idea that those people who are outwardly poor and wretched should be helped irrespective of what they are like inwardly; and that similarly widows and orphans should be helped solely because they are called such; and at length the idea that enemies in general should be helped irrespective of who they may be; and also the idea that by acting in these ways one is able to merit heaven. These and other ideas like them are the cognitions proper to the early childhood of his new life. They are such that because they derive to some extent from his previous life, or the disposition belonging to his previous life, they also derive to some extent from his new life into which he is being led in this way. They are consequently such as allow into themselves things that contribute towards the formation of a new will and of a new understanding. They are the lowest forms of good and truth, and it is with these that people who are being regenerated start out. And because these lowest forms of good and truth allow more interior truths into themselves, that is, truths closer to Divine truths, falsities which a person had previously believed to be truths are also rooted out.

[5] People who are being regenerated however do not learn such things simply as matters of knowledge but as matters of life, for they practice those truths. But their practice of them has its beginnings in the new will which the Lord is instilling, though they are totally unaware of it. And to the extent they welcome that new will they also welcome those cognitions, put them into practice, and believe them. But to the extent they do not welcome that new will they are indeed able to learn such truths but not to put them into effect since they consider them purely as matters of knowledge and not of life.

[6] That state is the state of early and later childhood as regards the new life which is to replace the previous life, but the state of the early and later youth of that life is a state when no attention is paid to any person's outward presentation of himself but to what he is like with regard to good - first of all with regard to it in public affairs, then in private affairs, and at length in spiritual, at which point he starts to possess and to love good first and foremost, and from good the person. And when after that he is more perfect still his concern is to aid those who are governed by good, his help depending on the kind of good present with those whom he helps. At length he takes delight in helping them. And because he takes delight in good he also takes pleasure in ideas that support it. Those supporting ideas he acknowledges as truths, which also constitute the truths of his new understanding which flow from the forms of good which belong to his new will.

[7] To the same extent as he takes delight in that good and takes pleasure in those truths he also feels an aversion to the evils of his previous life and a displeasure in its falsities. This is why things belonging to the previous will are now separated from those belonging to the new will, and those belonging to the previous understanding from those belonging to the new understanding. The determining factor in this separation is not the affection for knowing them, but the affection for doing them. As a consequence he now sees that the truths belonging to his early childhood in relation one to another have existed inversely and that those same truths have been reorganized little by little into another order, that is to say, their interrelationship has been changed so that those which initially occupied the first place now occupy the last. In this way he sees that by means of those truths which belonged to his early and later childhood the angels of God so to speak went up by means of a stairway from earth to heaven, whereas now by means of the truths belonging to his adult life the angels of God so to speak come down by means of the stairway from heaven to earth.