Jabir bin Abdullah (may Allah be pleased with them both) narrates that the Messenger of Allah (peace and blessings be upon him) entered upon Umm al-Sa'ib or Umm al-Musayyib (may Allah be pleased with her) while she was shivering. He (peace and blessings be upon him) said: "What is the matter with you, O Umm al-Sa'ib (or Umm al-Musayyib)?" She said: "It is the fever, may Allah not bless it." He (peace and blessings be upon him) said: "Do not curse the fever, for it removes the sins of the children of Adam just as the furnace removes the impurities of iron."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6561