(88) باب الْمَدِينَةِ تَنْفِي شِرَارَهَا
Jabir b. `Abdullah (Allah be pleased with them) reported that a desert Arab swore allegiance to Allah's Messenger (ﷺ). He suffered from a severe fever in Medina (and) so he came to Allah's Messenger (ﷺ) saying:
Muhammad, cancel my oath of allegiance. But Allah's Messenger (ﷺ) refused it. He again came and said: 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 Allah's Messenger (ﷺ) said: Medina is like a furnace which drives away its impurity and purifies what is good.
Reference: Sahih Muslim 1383
In-book reference: Book 15, Hadith 559
USC-MSA web (English) reference(deprecated numbering scheme): Book 7, Hadith 3191