Narrated Jabir bin 'Abdullah As-Salami:

A bedouin gave the Pledge of allegiance for embracing Islam to Allah's Apostle, and then he got an attack of fever in Medina and came to Allah's Apostle: and said, "O Allah's Apostle! Cancel my pledge." Allah's Apostle refused to do so. The bedouin came to him again and said, "Cancel my pledge," but he refused again, and then again, the bedouin came to him and said, "Cancel my pledge," and Allah's Apostle refused. The bedouin finally went away, and Allah's Apostle ﷺ said, "Medina is like a pair of bellows (furnace), it expels its impurities while it brightens and clears its good.' 9.424.:

Narrated Ibn 'Abbas: I used to teach Qur'an to 'Abdur-Rahman bin Auf. When Umar performed his last Hajj, 'Abdur-Rahman said (to me) at Mina, "Would that you had seen Chief of the believers today! A man came to him and said, "So-and-so has said, "If Chief of the Believers died, we will give the oath of allegiance to such-and-such person,' 'Umar said, 'I will get up tonight and warn those who want to usurp the people's rights.' I said, 'Do not do so, for the season (of Hajj) gathers the riffraff mob who will form the majority of your audience, and I am afraid that they will not understand (the meaning of) your saying properly and may spread (an incorrect statement) everywhere. You should wait till we reach Medina, the place of migration and the place of the Sunna (the Prophet's Traditions). There you will meet the companions of Allah's Apostle from the Muhajirin and the Ansar who will understand your statement and place it in its proper position' 'Umar said, 'By Allah, I shall do so the first time I stand (to address the people) in Medina.' When we reached Medina, 'Umar (in a Friday Khutba-sermon) said, "No doubt, Allah sent Muhammad with the Truth and revealed to him the Book (Quran), and among what was revealed, was the Verse of Ar-Rajm (stoning adulterers to death).'" (See Hadith No. 817,Vol. 8)

حَدَّثَنَا إِسْمَاعِيلُ، حَدَّثَنِي مَالِكٌ، عَنْ مُحَمَّدِ بْنِ الْمُنْكَدِرِ، عَنْ جَابِرِ بْنِ عَبْدِ اللَّهِ السَّلَمِيِّ، أَنَّ أَعْرَابِيًّا، بَايَعَ رَسُولَ اللَّهِ ﷺ عَلَى الإِسْلاَمِ، فَأَصَابَ الأَعْرَابِيَّ وَعْكٌ بِالْمَدِينَةِ، فَجَاءَ الأَعْرَابِيُّ إِلَى رَسُولِ اللَّهِ ﷺ فَقَالَ يَا رَسُولَ اللَّهِ 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 طِيبُهَا ".