In most commentaries there are discussions focused on the unity of composition (i.e., were there later editors?), date and purpose of the writing, questions of text preservation (consistency among known copies), underlying theology, and the “Sign of Jonah” from Matthew 12:40. If you are interested in a “deep dive” into some of these topics, any scholarly text will provide lots of details. Let me just provide a few thoughts – not trying to rehearse all the opinions and arguments, but simply offering what makes the most sense to me.
By no means is the date of original authorship easy to determine. There are lots of arguments about Nineveh – did it still exist or can it have already been destroyed (612 BCE) at the time of the composition of the book? Does it matter that the author spoke of the “King of Nineveh” instead of the “King of Assyria”? There are traces of Persian customs suggesting a later authorship somewhere in the mid-sixth to fourth century BCE – but that might be the work of a later editor. There are two references from the Book of Joel, which most scholars hold to be post-exilic, i.e., not earlier than 5th century BCE. There are questions of whether the original was in Aramaic and translated to Hebrew, or if the original Hebrew simply shows evidence of Aramaisms in language. There are a bevy of linguistic markers leading the scholarly community to lean towards a post-exilic date for authorship – that is, after the Jewish period of exile in Babylon. The book of Jonah was certainly known and accepted by 200 BCE according to Sirach 49:10. All-in-all, the book is probably best assigned to the fifth or fourth century BCE.
How about the purpose of the book? Most look to the last line. The verse is not only the climax of the book, but most offer it holds the key to its understanding:
“And should I not be concerned over Nineveh, the great city, in which there are more than a hundred and twenty thousand persons who cannot distinguish their right hand from their left, not to mention the many cattle?” (Jonah 4:11)
The majority of folks see it as addressing the idea that God’s embrace is for the Jewish people only (Jewish particularism) by emphasizing the all-embracing love of God for all people. Others offer up different central themes: justice vs. mercy without reference to particularism. Some suggest it is about Jonah’s willingness to hear the Word and be submissive as many other characters in the account. There are lots of other theories.
I would suggest the Jonah 4:11 is simply another instance of what the author has already raised for consideration when Jonah realized that God would not punish Nineveh: “I knew that you are a gracious and merciful God, slow to anger, rich in clemency, loathe to punish.” (Jonah 4:2) If a fundamental purpose of all of Scripture is to reveal God, this does it quite nicely. Seems like an adequate purpose of our times – and times past and future.
Which leads us to the “Sign of Jonah,” which for many Christians determines the significance of The Book of Jonah, holding that Jonah is a type of Christ – at least in the proto-resurrection from the belly of the fish. If so, then the book is reduced to a kind of “proof text” for Jesus’ Resurrection. If its purpose was simply to be a pointer to a resurrection, the book would have remained an enigma for Israel to whom the book was originally addressed. It would be a loss to stop reading at the end of Jonah 1 simply because one finds the Matthean reference verified.
The “sign of Jonah” is mentioned three times in the Gospels, twice in Matthew (12:38-41; 16:4) and once in Luke (11:29-32) – as well as indirectly perhaps in Mark 8:12 (“Why does this generation seek a sign? Amen, I say to you, no sign will be given to this generation.”).
A comparison of the two gospels is perhaps of interest:
38 Then some of the scribes and Pharisees said to him, “Teacher, we wish to see a sign from you.” 39 He said to them in reply, “An evil and unfaithful generation seeks a sign, but no sign will be given it except the sign of Jonah the prophet. 40 Just as Jonah was in the belly of the whale three days and three nights, so will the Son of Man be in the heart of the earth three days and three nights. 41 At the judgment, the men of Nineveh will arise with this generation and condemn it, because they repented at the preaching of Jonah; and there is something greater than Jonah here. 42 At the judgment the queen of the south will arise with this generation and condemn it, because she came from the ends of the earth to hear the wisdom of Solomon; and there is something greater than Solomon here (Mt 12:38-42)
28 He replied, “Rather, blessed are those who hear the word of God and observe it.” 29 While still more people gathered in the crowd, he said to them, “This generation is an evil generation; it seeks a sign, but no sign will be given it, except the sign of Jonah. 30 Just as Jonah became a sign to the Ninevites, so will the Son of Man be to this generation. 31 At the judgment the queen of the south will rise with the men of this generation and she will condemn them, because she came from the ends of the earth to hear the wisdom of Solomon, and there is something greater than Solomon here. 32 At the judgment the men of Nineveh will arise with this generation and condemn it, because at the preaching of Jonah they repented, and there is something greater than Jonah here. (Lk 11:28-32)
Matthew 12:40 is questioned by some scholars and thought to be a later interpolation. Justin Martyr did not include it in his early commentary on Matthew, plausibly because it was not part of the gospel available to him, the gospel not having reached final written form. Not convincing in itself, but one wonders why it is not part of Luke’s gospel given how similar the two passage are.
One view is to prefer the Lukan version and to interpret the sign in terms of Jesus’ preaching of repentance: those who hear the word of God and observe it. However, Jesus has already been preaching for some time, so it is unlikely that more preaching would be a sign to authenticate his ministry, whereas the resurrection fits well.
Another view is that Matthew has a different audience (Jewish not Gentile) and so is focused more on OT fulfillment and thus the focus on the miraculous as a sign of the Resurrection to come. The time reference of three days and nights is easily seen in terms of the Resurrection, but also remember that Jesus spoke of rebuilding the destroyed Temple in three days, referencing his rising from the dead. In other words, the phrase “three days” has literal and metaphoric usage.
Then again, looking to the original writing, one can ask what was the purpose of the fish/whale? Was it to be an instrument of punishment? Of death? Or deliverance from the grave? Leslie Allen notes: “A straightforward reading of Jonah 2 indicates that the use of Psalm 18 was meant as praise for deliverance not from the fish but from drowning. A number of scholars have perceived that the fish was not a means of punishing Jonah but a means of deliverance. …It is in fact more than this: the sailors in 1:13 could have done this just as well but were deliberately foiled. Jonah deserved to die, and the fish is Yahweh’s last-minute device to save him from merited death by drowning…The sea is the enemy, the bearer of death; the fish is Jonah’s ally by divine provision.” (op. cit.) In this understanding, the emphasis on the use of a psalm of thanksgiving is akin to a descent to the underworld (sheol). Such a descent is a constant feature of Hebrew psalmody to express the psalmist’s brush with death encountered in one form or another. The use of Psalm 18 (as well as Ps 42 and Ps 31)
“The cords of death encompassed me; the torrents of destruction terrified me… He reached down from on high and seized me; drew me out of the deep waters” (Ps 18:5,17)
It should be noted that the Psalm does not reference death and subsequent resurrection, but rather a deliverance from the drowning and death altogether. Then again, Jonah’s time under the sea afforded a close enough parallel to Jesus’ burial in the earth to generate the analogy used in Matthew 12:40.
All that being said, in Bible study, folks have said, “Ahhh… that’s nice. Was Jonah swallowed by the whale or not?” Something to remember when folks get focused on the “whale.” G. Campbell Morgan uttered a wise word: “Men have been looking so hard at the great fish that they have failed to see the great God.”
Leslie C. Allen, The Books of Joel, Obadiah, Jonah, and Micah part of The New International Commentary on the Old Testament (Grand Rapids, MI: Wm. B. Eerdmans Publishing Co., 1976
New American Bible, Confraternity of Christian Doctrine, 1996