Musnad Abu Ya'la al-Mawsili 109:175

Ibrahim al-Harawi narrated to us, Ismail bin Ibrahim narrated to us, al-Hajjaj bin Abi Uthman narrated to us, from Abu al-Zubayr, from Jabir, who said: A man came to Medina as an emigrant. He said: He was afflicted with a severe fever. He came to the Messenger of Allah, may Allah bless him and grant him peace, and said: "O Messenger of Allah, release me from the emigration." He said: "No, by Allah, I will not release you; indeed, Islam does not release." Al-Hajjaj said: And he mentioned that it was more than once, and each time he refused him. So he left without his permission. The Prophet, may Allah bless him and grant him peace, was informed of that, and he said: "Indeed, it is Taybah (Medina), it expels the filth of men just as the bellows expels the filth of iron."