A man said to the Messenger of Allah ﷺ, "What do you say about these illnesses that afflict us, what do we get from them?"He replied, "They are expiations."Ubayy said, "Even if they are slight?"He answered, "Even a thorn prick or anything greater than that."So Ubayy prayed against himself that fever would not leave him until he died, provided that it would not keep him from performing Hajj, Umrah, jihad in the way of Allah, or any obligatory prayer in congregation. No one ever touched him without feeling his heat, until he died.
أن رجلا قال لرسول الله ﷺ: أرأيت هذه الأمراض التي تصيبنا ما لنا بها؟ قال: كفارات. قال أبي: وإن قلت؟ قال: وإن شوكة فما فوقها. قال: فدعا أبي على نفسه أن لا يفارقه الوعك حتى يموت، في أن لا يشغله عن حج ولا عمرة ولا جهاد في سبيل الله، ولا صلاة مكتوبة في جماعة. فما مسه إنسان إلا وجد حره حتى مات.
Ahmad (11183) and Abu Yaala (995) both narrated it from Yahya bin Saeed, from Saad bin Ishaq, who said, "Zaynab, daughter of Kaab bin Ujra, narrated to me, from Abu Saeed Khudri," and mentioned it. Its chain is good, for there is disagreement about whether Zaynab, daughter of Kaab, was a companion, and the correct view is that she was a follower of the companions (tabiiyah). Two narrators transmitted from her, and Ibn Hibban deemed her trustworthy and included her hadith in his Sahih (2928), as did Hakim (4/308), who said, "Sahih according to the standard of the two Shaykhs." The correct view is that Zaynab, daughter of Kaab, who was the wife of Abu Saeed Khudri, was not included by the two Shaykhs. Haythami mentioned it in Majma (2/301-302) and said, "Ahmad and Abu Yaala narrated it, and its men are trustworthy."As for what was narrated from Muhammad bin Muaz bin Ubayy bin Kaab, from his father, from his grandfather, that he said, "I said, 'O Messenger of Allah, what is the reward for fever?' He said, 'Good deeds continue to accrue to the one afflicted by it for as long as a foot twitches upon him, or a vein throbs in him.'" Ubayy said, "O Allah, I ask You for a fever that does not prevent me from going out in Your cause, nor from going out to Your House, nor from going to the masjid of Your Prophet." And Ubayy never spent an evening without having a fever.This hadith contains an unknown narrator. Tabarani narrated it in Kabir and Awsat, and it contains Muhammad bin Muaz, who is unknown. Ibn Madini said, "We do not know Muhammad nor his father, and it is an unknown chain." The Hafiz mentioned him... The Hafiz mentioned him in Taqrib. Muhammad is the son of Muaz bin Muhammad bin Ubayy bin Kaab, so his saying "from his grandfather" means the grandfather of his father.