Musnad Ahmad 33:278

Abu Mu'awiyah narrated to us, from al-A'mash, from Abu Sufyan, from Jabir, who said: The fever asked permission of the Prophet, may Allah bless him and grant him peace. He said: "Who is this?" It said: "Umm Mildam." He said: So he ordered it to go to the people of Quba, and they suffered from it what Allah knows. They came to him and complained about that to him. He said: "What do you wish? If you wish, I will supplicate to Allah for you, and He will remove it from you. And if you wish, it will be a purification for you." They said: "O Messenger of Allah, will you do that?" He said: "Yes." They said: "Then leave it."