It is narrated from Sayyiduna Jabir (may Allah be pleased with him) that the fever came to the Prophet (peace and blessings be upon him) and asked permission (to enter). He (peace and blessings be upon him) said: "Who are you?" It said: "I am the fever." He (peace and blessings be upon him) said: "Do you know the people of Quba?" It said: "Yes." So he (peace and blessings be upon him) said: "Go to them." So it went to them, and they felt its severity, so they complained to him (peace and blessings be upon him). He (peace and blessings be upon him) said: "If you wish, I will supplicate to Allah Almighty and He will remove it from you; and if you wish, it will become for you a purification (tahur) and an expiation for sins." They said: "Rather, being an expiation and a means of purification is better."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6550