It is narrated from Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) went in to one of his household who was suffering from fever. The Prophet (peace and blessings be upon him) asked: "Is this Umm Mildam (fever)?" A woman said: Yes, may Allah curse it. So the Prophet (peace and blessings be upon him) said: "Do not curse it, for it washes away (or: removes) the sins of the children of Adam just as the furnace removes the impurities of iron." This hadith is sahih (authentic) on the condition of Muslim; there is no hidden defect in it, but the two Shaykhs (Bukhari and Muslim) did not record it.