Musannaf Ibn Abi Shayba 27:788

Al-Fadl ibn Dukayn narrated to us, from Sufyan, from Muhammad ibn al-Munkadir, who said: I heard Jabir, from the Prophet, peace and blessings of Allah be upon him, who said: "Al-Madinah is like the bellows; it expels its filth and purifies its good."