Abu Huraira reported God's messenger as saying, “The last hour will not come before Medina drives away its wicked people as the bellows drives away the impurity of iron." Muslim transmitted it.

وَعَنْ أَبِي هُرَيْرَةَ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «لَا تَقُومُ السَّاعَةُ حَتَّى تَنْفِيَ الْمَدِينَةُ شِرَارَهَا كَمَا يَنْفِي الْكِيرُ خَبَثَ الْحَدِيد» . رَوَاهُ مُسلم