Sayyiduna Salman (may Allah be pleased with him) narrated: Fever sought permission from the Messenger of Allah (peace and blessings be upon him) to come in, and he (peace and blessings be upon him) asked it: "Who are you?" It said: I am fever; I melt away the flesh and suck the blood. He (peace and blessings be upon him) said: "Go to the people of Quba." So it went to them. They came to the Prophet (peace and blessings be upon him) with their faces turned pale, and complained to the Messenger of Allah (peace and blessings be upon him) about the fever. He (peace and blessings be upon him) said: "As you wish: if you wish, I will supplicate to Allah to remove it from you; and if you wish, leave it, so that it may cause the rest of your sins to fall away." They said: O Messenger of Allah! Rather, leave it be.
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6088