The New Testament doesn’t say much about the prophet Jonah, although the little it does say has made him an important figure in Christianity, his time spent inside the fish prefiguring the death and resurrection of Jesus.
The only references to Jonah in the New Testament are in a saying by Jesus recorded in both Matthew and Luke. The two accounts are similar although different so I put them both below with the words they have in common highlighted in red.
MATTHEW 14:39-41; 16:4
But he [Jesus] answered them, “An evil and adulterous generation seeks for a sign, but no sign will be given to it except the sign of the prophet Jonah. 40For just as Jonah was three days and three nights in the belly of the great fish, so will the Son of Man be three days and three nights in the heart of the earth. 41The men of Nineveh will rise up at the judgment with this generation and condemn it, for they repented at the preaching of Jonah, and behold, something greater than Jonah is here.
… 16:4 An evil and adulterous generation seeks for a sign, but no sign will be given to it except the sign of Jonah.” So he left them and departed.
When the crowds were increasing, he [Jesus] began to say, “This generation is an evil generation. It seeks for a sign, but no sign will be given to it except the sign of Jonah. 30For as Jonah became a sign to the people of Nineveh, so will the Son of Man be to this generation…32The men of Nineveh will rise up at the judgment with this generation and condemn it, for they repented at the preaching of Jonah, and behold, something greater than Jonah is here.
It can be seen that the words in red are common to both Matthew and Luke, but in both accounts they are ‘split’ with different words in between. So which of the two accounts records the actual saying of Jesus? The most likely explanation in my view is that the words in red are the ‘actual’ saying of Jesus and that both Matthew and Luke have copied them from a source which they both accessed. There is a widely held view amongst New Testament scholars (known as the “two source hypothesis”) that when Matthew and Luke were written the writers had two written sources in front of them: one was the gospel of Mark, as large parts of Mark appear word-for-word in both Matthew and Luke; the other was an unknown source which scholars often call ‘Q’ which is an abbreviation of the German word Quelle, or ‘source’. If we compare Matthew and Luke in their entirety we discover that much of these two gospels are identical. If we extract those sections which are identical to Mark the remainder is what scholars call Q. An interesting thing about Q is that it consists primarily of sayings of Jesus, with no narrative. It appears that at some stage, before Matthew and Luke were written (although possibly after Mark) a document was written which listed many of the sayings of Jesus, and this is what we now call Q. It doesn’t exist any more, or at least it hasn’t been found anywhere. But who knows, maybe it will turn up some day in a monastic library (like some of the best manuscripts available of the New Testament) or in a Judean cave (like the Dead Sea Scrolls). It appears that another very early Christian text called the Didache, or teachings of the apostles, may also have used Q as a source, but that is another discussion to be had.
It would be a reasonable explanation then that the actual saying of Jesus which may have been sourced from Q went like this:
An evil and adulterous generation seeks for a sign, but no sign will be given to it except the sign of the prophet Jonah. The men of Nineveh will rise up at the judgment with this generation and condemn it, for they repented at the preaching of Jonah, and behold, something greater than Jonah is here.
The problem is, this leaves the reader to guess what this “sign of Jonah” was. Both Matthew and Luke inserted their own explanations into their accounts. This isn’t uncommon as we see this kind of thing happening quite a bit in ancient texts which quoted from earlier ones. In this case, however, Matthew and Luke provide different explanations for Jesus’ saying. Matthew says the sign would be “just as Jonah was three days and three nights in the belly of the great fish, so will the Son of Man be three days and three nights in the heart of the earth.” Luke on the other hand says “as Jonah became a sign to the people of Nineveh, so will the Son of Man be to this generation.” We don’t have a case of the two writers recording Jesus’ saying differently (and hence one or both of them ‘misquoting’ Jesus) but of them both recording the same saying but inserting their own explanations, and these explanations differed.
The modern reader is still left to wonder what the “sign of Jonah” meant as the two explanations are different. Luke’s explanation isn’t that different from the saying of Jesus as it focussed on the people of Nineveh and their reaction to Jonah’s preaching. But Matthew’s explanation steps right away from this and offers an allegorical interpretation of the story of Jonah. It is not surprising that a story as strange as Jonah’s which has a host of unusual features (such as someone surviving inside a fish for three days) would attract an allegorical interpretation, and there is evidence in Rabbinic sources that this method of interpretation was applied from an early time. One interpretation, for example, is that Jonah represents Israel and as he was vomited by the fish so Israel was ‘vomited’ from their land when they went into captivity. Leviticus 18 uses precisely this kind of language to describe the land of Canaan vomiting out its inhabitants (18:25) and threatens the same for Israel if they do not keep the statutes and commandments God has given them: “lest the land vomit you out for defiling it, as it vomited out the nation that was before you” (18:28).
Jeremiah 51 portrays Nebuchadnezzar and Bel the god of Babylon as sea monsters that have “swallowed up” Israel: “he has swallowed me like a monster; he has filled his belly with my delicacies, he has spewed me out” (Jeremiah 51:34). Jeremiah use the same word that occurs in Jonah 1:17 for the fish swallowing Jonah (although it uses a different word for vomitting, and “sea monster”), and this may be further evidence that Jonah presents an image of Israel being vomitted out of captivity after being swallowed by the Babylonians. This doesn’t necessarily mean we should interpret Jonah allegorically, although it seems that some of the early Rabbis and Matthew did to some extent. It could be an allusion by the writer of Jonah to both the Leviticus and Jeremiah texts recalling the experiences of Israel being “spewed” from place to place as they go into exile and then being disgorged again by Babylon.
Matthew’s interpretation is similarly somewhat allegorical and adds another level of meaning. This is not to suggest that this was the original intention or meaning of Jonah, as we have clear evidence in the way the New Testament quotes the Hebrew Bible (and also in the way some of the Dead Sea Scrolls quote the Hebrew Bible) that later writers often re-interpreted earlier texts, giving them ‘new’ meanings which were appropriate to their own circumstances and relevant to their audiences. So Matthew gives a new meaning to the Jonah story for his audience. He saw a connection to Jesus’ resurrection while Luke apparently didn’t make the same connection. It suggests there is no ‘right’ way to read many of the stories in the Bible. For Matthew there was one way, for Luke another. Perhaps we can learn something from this when we try to make an argument from the Bible; that even the writers of the Bible read earlier biblical books in different ways.