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.

4925. 'That behold, his brother came out' means the truth of good. This is clear from the meaning of 'brother' as that which is kindred, by virtue of good, dealt with in 3815, 4267, and so the truth of good. The truth of good is that truth which is rooted in good, or that faith which is rooted in charity. Dealt with here in the internal sense is the birthright in the case of those who are being born again or regenerated by the Lord, and therefore the birthright within the Church. It has been a matter of argument since most ancient times as to which is the firstborn, whether this is the good of charity or whether it is the truth of faith. Unseen while a person is being born again and becoming a Church, good conceals itself within the interior man and reveals itself solely within some affection which does not pass into the conscious feelings of the external or natural man until he has been born again. But truth reveals itself, for this does enter his conscious feelings and lodges in the memory belonging to the external or natural man. This explains why many have fallen into the error that truth is the firstborn, and at length even thinking that truth is the vital element of the Church, so vital that truth which is called faith can save a person without the good of charity.

[2] From this one error very many others have been derived which have infected not only what is taught but also life, such as the error that no matter what kind of life a person leads he can be saved provided he has faith. A further derivative error is that very wicked people are accepted into heaven provided that in the final hour before they die they declare their belief in those things which are matters of faith; and another such error is that, irrespective of the kind of life one has led, one is accepted into heaven solely by grace. Because people hold to this teaching they fail at length to know what charity is or to have any concern about what it is, till in the end they do not believe in the existence of it, or consequently in the existence of heaven and hell. The reason for this is that faith without charity, or truth without good, teaches a person nothing; and the more it departs from good, the more foolish it makes him. For good is what the Lord flows into and through which He flows, imparting intelligence and wisdom and consequently a superior ability to see, and also perception whether something is really true or not.

[3] From these considerations one may now see the position with regard to the birthright, namely that in actual fact it belongs to good but appears to belong to truth. This is what the birth of Tamar's two sons is used to describe in the internal sense. 'The twice-dyed thread' which the midwife bound on the hand that came out means good, as shown in 4922; 'coming out first' means priority of place, 4923; 'withdrawing the hand' means that good concealed its own power, as stated immediately above [in 4924]; 'his brother came out' means truth; 'you have made a breach upon yourself means this truth's apparent separation from good; 'afterwards his brother came out' means that good is in actual fact first; and 'on whose hand was the twice-dyed thread' means the acknowledgement that good is first. For it is not until after a person has been born again that good is acknowledged to be first, at which point that person's actions spring from good, and his view of truth and what this is like springs from the same.

[4] These are the matters contained within the internal sense, in which teaching is given regarding the good and truth with a person who is being born anew, namely that good in actual fact occupies first place but truth appears to do so, and that good is not seen to occupy the first place while a person is being regenerated but is plainly seen to do so once he has been regenerated. But there is no need to explain these matters any further since they have been explained already - see 3324, 3325, 3494, 3539, 3548, 3556, 3563, 3570, 3576, 3603, 3701, 4243, 4244, 4247, 4337; and the fact that controversy has taken place since ancient times over whether the birthright belonged to good or to truth, that is, to charity or to faith, 2435.

[5] Because in the highest sense the Lord is the firstborn, and therefore love to Him and charity towards the neighbour are the firstborn, the law was for that reason laid down in the representative Church that firstborn things were Jehovah's: in Moses,

Sanctify to Me all the firstborn, that which opens the womb among the children of Israel; with man and with beast let them be Mine. Exodus 13:2.

You shall make over to Jehovah all that opens the worm', and every firstling of a beast; however many males you have they shall be Jehovah's. Exodus 13:12.

All that opens the womb is Mine; therefore among all your cattle, you shall give the male. that among oxen and small cattle which opens [the womb]. Exodus 34:19.

All that opens the womb among all flesh which they bring to Jehovah, from men and from beasts, shall be yours. Nevertheless you shall surely redeem all the firstborn of men. Numbers 18:15.

Behold, I Myself have taken the Levites from the midst of the children of Israel, instead of every firstborn, that which opens the womb, from the children of Israel, so that the Levites may be Mine. Numbers 3:12.

[6] Because the firstborn is the one that opens the womb, the expression 'that which opens the womb' is therefore added, when the firstborn is mentioned in these places, so as to mean good. It is evident that this expression means good from the specific details contained in the internal sense, especially from those which are recorded regarding the sons of Tamar: Zerah is said to have opened the womb with his hand, and 'Zerah' represents good, as is also clear from the twice-dyed thread placed on his hand, dealt with in 4922. In addition to this 'the womb', to which the expression 'opened' is applied, means the place where good and truth, consequently the Church, lie, see 4918, while 'opening the womb' means supplying the power which enables truth to be born.

[7] Because the Lord is the only firstborn - He being Good itself, and His Good being the source of all truth - Jacob, who was not the firstborn, was therefore allowed to purchase the birthright from Esau his brother so that he might represent Him. Also, because this was not sufficient, he was called Israel, so that by this name he might represent the good of truth; for 'Israel' in the representative sense means good which comes through truth, 3654, 4286, 4598.