Jabir bin Abdullah (may Allah be pleased with him) narrated that the Messenger of Allah (peace be upon him) entered upon Umm As-Sa’ib or Umm Al-Musayyab, and said: “What is matter with you O Umm As-Sa’ib (or Umm Al-Musayyab)? Why are you shivering?” She said: “I have a fever, may Allah not bless it!” He (peace be upon him) said:

“Do not revile (curse) fever, for it takes away the sins of the sons of the Adam as the bellows (furnace) takes away the dross (waste) of iron.”

[Sahih Muslim, Book of Al-Birr (1), Hadith: 6570]