“The men of Nineveh will arise in the judgment with this generation, and will condemn it, for they repented at the preaching of Jonah, and behold, a greater than Jonah is here.”
The second, but lesser, sign lay in Jonah's evangelistic ministry. Jonah had gone to Nineveh and there had been a great revival with many repenting. But it was short and sweet. John had done the same thing in Judea but over a longer period, and bringing far more to repentance. Jesus, however, had outshone them both (see John 4:1). Thus it should have been clear to all that ‘a greater than Jonah' was here. That is why the Gentile Ninevites will stand up or arise (anistemi - ‘rise') at the judgment and pass judgment on Jesus' generation, for even though they saw none of the signs and wonders that were now being seen, yet they had repented in their thousands. As resurrected saints they will not be able to credit how the Jews could have rejected Jesus, and will condemn them. Note that they will be there as those who are truly believers. They are not like the Tyre, Sidon and Sodom of the past.
‘A greater.' Literally ‘something greater'. Jesus is not only a greater prophet, He is greater in an even more distinctive way. Compare Matthew 12:6.