Luke 11:30

“For even as Jonah became a sign to the Ninevites, so will also the Son of man be to this generation.”

The crowds knew that Jonah had arrived in Nineveh having spent three days in the innards of a large fish like creature. He had been dead and had come alive. (He also probably looked inhumanly pale and somewhat strange as a result of the chemical action that would have affected his skin, and the account of his emergence from the fish after three days would have added to the effect). Given that he was also dressed as a Hebrew prophet he had come as ‘a sign' from the dead to the Ninevites. The result was that they had attended to his words and had repented of their sin and idolatry.

In their eyes (and in the eyes of the crowds) here was a man who had come back from a watery grave. All would have heard the word that could hardly have failed to get around that this weird and unearthly looking man who had appeared before them had been ‘dead' for three days in the body of a great fish. (The reasonable assumption is that Jonah would have told some of them of his experience. Indeed it can hardly be doubted). Thus they would see him as bringing them words from beyond the grave.

We can imagine what happened. Jonah takes up accommodation somewhere in Nineveh. They ask him why his skin is such a strange colour. He explains what had happened to him in his being swallowed by a huge fish and how he had prayed from the world of darkness. They go around telling their associates about this Hebrew prophet who has come back from the watery depths, even from the very dead. Thus soon crowds gather to see him, and awed by his pale and strange looking skin, and the even stranger tale that they have been told, they take careful heed to his words so that God moves their hearts and a great movement of the word of God takes place. He was indeed ‘a sign' to them.

In the same way Jesus promises that the Son of Man ‘will be' a sign to this generation. This would suggest that in some way He too would to come back from the dead after three days. This would not have seemed quite so impossible to them as we might think, for they knew that the Scriptures taught what had happened to the ‘son of man'. He had come from the midst of awful persecution and death (Luke 7:21; Luke 7:25), in order to make His way triumphantly to the throne of God, so that He might receive Kingly Rule (Luke 7:13), having necessarily been involved in the resurrection from the dead (Daniel 12:1). Like Jonah He too would then become a ‘sign' (compare John 2:18).

Some consider that Luke is referring to Jonah's preaching as the sign, and that he was suggesting that Jesus meant that His own preaching was similarly a sign, ‘the sign of the prophet Jonah' signifying ‘the same kind of sign as the prophet Jonah'. Certainly Jonah's preaching had been hugely successful, and equally certainly Jesus' teaching was. But successful preaching is never called a sign, and it does not explain why Jesus chose Jonah as His illustration. Other prophets were seen as having been successful. Furthermore it is Jonah himself who is quite clearly called the sign, ‘the sign of Jonah'. For his preaching was successful because the Ninevites saw him as a sign, not the other way round. It also explains Jesus' use of the future tense when speaking of Himself as a sign. For He had clearly indicated that He was not in the present willing to give any further sign than the ones they continually saw in His preaching and casting out of evil spirits (see Mark 8:12).

And there is no question but that the crowd listening to Jesus would, when thinking of Jonah, think in terms of his awesome experience, and see that as a sign. It was both vivid and memorable. So ‘the sign of Jonah' gave them a clue as to what to look for. Jesus was promising that He too would at some stage arrive back from the dead. While it was a sign not yet given, it was a sign that He assured them would be given. He would thus become a sign to His generation. For such a future event as a sign we can compare Exodus 3:12.

The book of Acts undoubtedly reveals precisely that, that the resurrection became a sign spoke of and witnessed to by the Apostles, who saw it as a foundational part of their preaching and a sign of Who Jesus was.