The Messenger of Allah ﷺ said, "When any of you has a fever, let him pour water over himself for three nights at the time before dawn."
أن رسول الله ﷺ قال: إذا حم أحدكم فليسن عليه الماء ثلاث ليال من السحر.
No references are available.
Abu Yaala (3794) narrated it from Harun bin Hammal, who said, Rawh bin Ubada told us, Hammad bin Salama told us, Humayd informed us, from Anas, and he mentioned it. Its chain is sahih. Nasai also narrated it in Kubra (7612), and Hakim graded it sahih (4/200-201), as did Diya in Mukhtara (2044, 2045), all of them through routes from Ibn Ayesha, who is Ubaydullah bin Muhammad bin Ayesha, so named in relation to Ayesha bint Talha because he descends from her, though his grandfather's actual name was Hafs bin Umar bin Musa Taymi, who is also trustworthy. Ibn Hajar strengthened its chain in Fath al-Bari (10/177).However, Abu Hatim and Abu Zura preferred the view that Hammad bin Salama narrated it from Humayd, from Hasan, in mursal form. Ilal al-Hadith (2/337). There is nothing preventing both routes from being preserved, since Humayd heard from his teacher Anas just as he heard from his teacher Hasan. Allah, the Exalted, knows best.As for what is narrated from Thawban, that the Prophet ﷺ said, "When fever strikes one of you, and fever is a piece of the Fire, let him extinguish it with water. Let him immerse himself in a flowing river, facing the current, and say, In the name of Allah, O Allah, heal Your servant and confirm the truth of Your Messenger, after the Fajr prayer before sunrise. Let him dip himself in it three times over three days. If he is not cured within three days, then five, and if he is not cured within five, then seven, and if he is not cured within seven, then nine, for it rarely exceeds nine, by Allah's permission," this is daif.It was narrated by Tirmidhi (2084) and Ahmad (22425), both from the hadith of Rawh bin Ubada, who said, Marzuq Abu Abdullah Shami told us, a man from the people of Syria told us, who said, Thawban informed us, and he mentioned it. This is how it appears in Tirmidhi, "a man from the people of Syria," and his name is Saeed as given in Musnad Ahmad, and he is Saeed bin Zura Shami as recorded in Tabarani (2/100). Bukhari mentioned him in Tarikh al-Kabir (3/466-468), saying, "Saeed Himsi Shami," then he cited the hadith through the route of Rawh bin Ubada, then said, "If it is not Ibn Zura, then I do not know."I say, he is unknown, for I have not found anyone who established his reliability. Mizzi, in his Tahdhib, quoted Abu Hatim as saying, "Unknown." But after reviewing the commentary in Tarikh al-Kabir, it became clear that he is a different man from the teacher of Marzuq, even though both of them were from Syria.