Al-Madinah eliminates its Dross and it is also called Tabah, and Taibah

Abu Huraira (Allah be pleased with him) reported Messenger of Allah ﷺ as saying: A time will come for the people (of Medina) when a man will invite his cousin and any other near relation: Come (and settle) at (a place) where living is cheap, come to where there is plenty, but Medina will be better for them;
would they know it! By Him in Whose Hand is my life, none amongst them would go out (of the city) with a dislike for it, but Allah would make his successor in it someone better than be. Behold. Medina is like furnace which eliminates from it the impurities. And the Last Hour will not come until Medina banishes its evils just as a furnace eliminates the impurities of iron.

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا عَبْدُ الْعَزِيزِ، - يَعْنِي الدَّرَاوَرْدِيَّ - عَنِ الْعَلاَءِ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ " يَأْتِي عَلَى النَّاسِ زَمَانٌ يَدْعُو الرَّجُلُ ابْنَ عَمِّهِ وَقَرِيبَهُ هَلُمَّ إِلَى الرَّخَاءِ هَلُمَّ إِلَى الرَّخَاءِ وَالْمَدِينَةُ خَيْرٌ لَهُمْ لَوْ كَانُوا يَعْلَمُونَ وَالَّذِي نَفْسِي بِيَدِهِ لاَ يَخْرُجُ مِنْهُمْ أَحَدٌ رَغْبَةً عَنْهَا إِلاَّ أَخْلَفَ اللَّهُ فِيهَا خَيْرًا مِنْهُ أَلاَ إِنَّ الْمَدِينَةَ كَالْكِيرِ تُخْرِجُ الْخَبِيثَ . لاَ تَقُومُ السَّاعَةُ حَتَّى تَنْفِيَ الْمَدِينَةُ شِرَارَهَا كَمَا يَنْفِي الْكِيرُ خَبَثَ الْحَدِيدِ " .

Abu Huraira (Allah be pleased with him) reported Allah's Messenger ﷺ as saying: I have been commanded (to migrate) to a town (Medina) which would overpower other towns. They (the people) call it Yathrib;
its correct name is (in fact) Medina. It eliminates (bad) people just as a furnace removes the alloy of iron.

وَحَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، عَنْ مَالِكِ بْنِ أَنَسٍ، - فِيمَا قُرِئَ عَلَيْهِ - عَنْ يَحْيَى بْنِ، سَعِيدٍ قَالَ سَمِعْتُ أَبَا الْحُبَابِ، سَعِيدَ بْنَ يَسَارٍ يَقُولُ سَمِعْتُ أَبَا هُرَيْرَةَ، يَقُولُ قَالَ رَسُولُ اللَّهِ ﷺ " أُمِرْتُ بِقَرْيَةٍ تَأْكُلُ الْقُرَى يَقُولُونَ يَثْرِبَ وَهْىَ الْمَدِينَةُ تَنْفِي النَّاسَ كَمَا يَنْفِي الْكِيرُ خَبَثَ الْحَدِيدِ " .

This hadith has been narrated by Yabya b. Sa'id with the same chain of transmitters (and the words are):" Just as a furance removes impurity," but no mention is made of iron.

وَحَدَّثَنَا عَمْرٌو النَّاقِدُ، وَابْنُ أَبِي عُمَرَ، قَالاَ حَدَّثَنَا سُفْيَانُ، ح وَحَدَّثَنَا ابْنُ الْمُثَنَّى، حَدَّثَنَا عَبْدُ الْوَهَّابِ، جَمِيعًا عَنْ يَحْيَى بْنِ سَعِيدٍ، بِهَذَا الإِسْنَادِ وَقَالاَ " كَمَا يَنْفِي الْكِيرُ الْخَبَثَ " . لَمْ يَذْكُرَا الْحَدِيدَ .

Jabir b. Abdullah (Allah be pleased with them) reported that a desert Arab swore allegiance to Messenger of Allah ﷺ. He suffered frozn a severe fever in Medina (and) so he came to Messenger of Allah ﷺ saying: Mubammad. cancel my oath of allegiance, but Messenger of Allah ﷺ refused it. He again came and caid: Cancel my oath of allegiance. but he (the Holy Prophet) refused it. He again came to him and said: Cancel my oath of allegiance, but he refused. The desert Arab, however, went away (cancelling the allegiance himself) ;
thereupon Messenger of Allah ﷺ said: Medina is like a furnace which drives away its impurity and purifies what is good.

حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنْ مُحَمَّدِ بْنِ الْمُنْكَدِرِ، عَنْ جَابِرِ، بْنِ عَبْدِ اللَّهِ أَنَّ أَعْرَابِيًّا، بَايَعَ رَسُولَ اللَّهِ ﷺ فَأَصَابَ الأَعْرَابِيَّ وَعَكٌ بِالْمَدِينَةِ فَأَتَى النَّبِيَّ ﷺ فَقَالَ يَا مُحَمَّدُ أَقِلْنِي بَيْعَتِي . فَأَبَى رَسُولُ اللَّهِ ﷺ ثُمَّ جَاءَهُ فَقَالَ أَقِلْنِي بَيْعَتِي . فَأَبَى ثُمَّ جَاءَهُ فَقَالَ أَقِلْنِي بَيْعَتِي . فَأَبَى فَخَرَجَ الأَعْرَابِيُّ فَقَالَ رَسُولُ اللَّهِ ﷺ " إِنَّمَا الْمَدِينَةُ كَالْكِيرِ تَنْفِي خَبَثَهَا وَيَنْصَعُ طَيِّبُهَا " .

Zaid b. Thabit reported Allah's Apostle ﷺ as saying: It is Taiba, thereby meaning Medina. It drives away impurity just as fire removes the impurity of silver.

وَحَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ مُعَاذٍ، - وَهُوَ الْعَنْبَرِيُّ - حَدَّثَنَا أَبِي، حَدَّثَنَا شُعْبَةُ، عَنْ عَدِيٍّ، - وَهُوَ ابْنُ ثَابِتٍ - سَمِعَ عَبْدَ اللَّهِ بْنَ يَزِيدَ، عَنْ زَيْدِ بْنِ ثَابِتٍ، عَنِ النَّبِيِّ ﷺ قَالَ " إِنَّهَا طَيْبَةُ - يَعْنِي الْمَدِينَةَ - وَإِنَّهَا تَنْفِي الْخَبَثَ كَمَا تَنْفِي النَّارُ خَبَثَ الْفِضَّةِ" .