“On the Judgment Day the people of Nineveh will stand up and accuse you, because they turned from their sins when they heard Jonah preach; and I tell you that there is something here greater than Jonah! On the Judgment Day the Queen of Sheba will stand up and accuse you, because she traveled all the way from her country to listen to King Solomon's wise teaching; and I assure you that there is something here greater than Solomon!” Matthew 12:41-42 GNT
The mention of Jonah brings the story of Jonah to mind, and so Jesus makes a point of the heart of that account. The people of Israel were both affluent and indifferent to the call of God on their lives to be a light to the nation. So God called the reluctant prophet to go and preach to the hated enemies of Israel, the Assyrians who lived in Nineveh (modern Iraq). But the point of the story is that those people repented at the preaching of Jonah, and God spared that generation the judgment.
Jesus says that those people of Nineveh will “stand up” at the judgment and “condemn” these unbelievers. Well, it will be God who judges unbelieving sinners — so what does this line mean? I think the point that Jesus was making was that here were people from other nations who had far less revelation than Jesus’ opponents, but they believed the word of the Lord.
The fact that they will “rise up” (meaning stand, i.e., not fall, not be condemned) in the judgment will be evidence that people of Jesus’ day could have believed without all this convincing. In other words, their conversion will be a condemnation for unbelieving Israel. If they could believe, why could not the Jews?
The second story is the visit of the Queen of Sheba who came to challenge Solomon’s wisdom. Of course, he made a believer out of her by answering all her questions. Here was a queen from another land, not an Israelite, who had very little information other than that the wisdom of God was in this king, and she came, she heard, and she was convinced. Her presence in the kingdom will also condemn Israel, for if she could believe what she heard about God’s wisdom in Solomon after a brief visit, if she could believe with what she had, they should have believed with all that they had. For Jesus is far greater than Solomon.
So Jesus made this striking point that the stakes are now much higher. Pagans believed in the Lord at the preaching of Jonah--but Jesus is much greater than Jonah. He preached far more profound things, and did amazing miracles to authenticate His words. They should have believed. A pagan queen believed because she heard wise sayings from the king of Israel--but Jesus is far greater than Solomon. His wisdom and His knowledge surpasses them all. They should have believed.
So in the judgment they will be condemned for their unbelief very convincingly because people like this with little or no information believed, whereas they with the presence of the Lord in their very midst refused to believe.