Demand for signs and punishment as proof

قَالُوٓا۟ أَجِئْتَنَا لِنَعْبُدَ ٱللَّهَ وَحْدَهُۥ وَنَذَرَ مَا كَانَ يَعْبُدُ ءَابَآؤُنَا ۖ فَأْتِنَا بِمَا تَعِدُنَآ إِن كُنتَ مِنَ ٱلصَّـٰدِقِينَ

They said, "Have you come to us that we should worship Allāh alone and leave what our fathers have worshipped? Then bring us what you promise us, if you should be of the truthful."