Illness as expiation, the reward of the sick, and that the believer is tried severely to increase his reward

It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him): I was sitting in the gathering of the Messenger of Allah (peace and blessings be upon him) when he (peace and blessings be upon him) began to smile. We said: O Messenger of Allah! What made you smile? He (peace and blessings be upon him) said: "I was amazed at the believer and his distress at illness; yet if he knew how much reward there is for him in illness, he would love to remain ill until he meets his Lord." Then he (peace and blessings be upon him) smiled a second time, raised his blessed head towards the sky and looked at it. The Companions said: O Messenger of Allah! What made you smile? He (peace and blessings be upon him) said: "I was amazed at two angels who came down from the sky and began searching for a believing servant at his place of prayer where he used to pray, but they did not find him there. So they ascended to the presence of Allah Almighty and said: 'O our Lord! Your servant so-and-so, for whom we used to record such-and-such good deeds every day, You have confined him in Your ropes,' meaning You have afflicted him with illness. Allah Almighty said to the two angels: 'Write for My servant the same deeds as he used to do (in health) every day and night, and do not reduce anything from it; for him is the reward of the deeds he used to do and also the reward of the trial in which I have confined him.'"
Al-Tayalisi also recorded it through the chain of Muhammad bin Abi Humayd. This hadith is weak in its chain.

It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Indeed, a man has a special lofty rank and station with Allah Almighty which he cannot reach merely through his deeds, until he is afflicted with some trial and pain in his body; and so through that trial he reaches that (appointed) rank."
Its chain is weak.
Also, Abu Bakr, in his narration from Abu Mu'awiyah, added an (unnamed) intermediary between Jabalah and Ibn Mas'ud, who had informed him (Jabalah).

Abu Burdah (may Allah have mercy on him) narrates from one of the Mothers of the Believers (may Allah be pleased with them) that the Messenger of Allah (peace and blessings be upon him) fell ill and the pain of his illness became very severe. When he (peace and blessings be upon him) recovered somewhat, I said: If one of us (women) had suffered pain like this, I would have feared (danger) for her. At this he (peace and blessings be upon him) said: "Do you not know that the believer's illness and pain are made severe so that the burden of his sins may be removed from him in return?"
Musaddad recorded it in his Musnad, and its chain is jayyid (good).

It is narrated from Abu al-Ash'ath al-San'ani (may Allah have mercy on him) that he set out for the Grand Mosque of Damascus and arrived there at midday. There he met Sayyiduna Shaddad bin Aws (may Allah be pleased with him) and another man with him, and he asked: "May Allah have mercy on you both, where are you intending to go?" They both replied: "We are going here to visit a sick brother of ours." The narrator says: So he went along with them until they reached that sick man, and the two of them asked him: "How have you woken this morning?" He replied: "I have woken by the blessing of Allah and His bounty." At this Sayyiduna Shaddad (may Allah be pleased with him) said to him: "Rejoice at the expiation of sins and the shedding of faults, for I heard the Messenger of Allah (peace and blessings be upon him) saying: 'Allah, the Mighty and Majestic, says: Indeed, when I afflict one of My believing servants with a trial (of illness) and he praises Me for that trial, he rises from that bed of his as clean of sins as on the day his mother gave birth to him. And Allah, the Mighty and Majestic, says (to the angels): It is I who confined this servant of Mine and put him to trial, so continue for him the same reward that you used to continue for him in his state of health and well-being.'"
In the chain of this report in Musnad Abi Ya'la, there is criticism of Isma'il bin Ayyash's narration from Rashid bin Dawud; however, on the basis of other supporting reports this hadith reaches the grade of sahih li-ghayrihi (authentic due to supporting evidence).

It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) passed by a tree and shook it (holding it) until as many of its leaves fell as Allah Almighty willed to fall. Then he (peace and blessings be upon him) said: "Pains and calamities are far quicker in erasing the sins of the son of Adam than I was (in shaking off the leaves of) this tree."
Musnad Abi Ya'la: 2455. Its chain has weakness because of Jabir al-Ju'fi and Ziyad al-Numayri.

Sayyiduna Anas (may Allah be pleased with him) said: "The example of the believer is like an ear of grain; sometimes it bends and sometimes it stands upright."

It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Indeed, (sometimes) a man has a lofty station and rank (appointed) with Allah Almighty which he cannot reach merely through his deeds; so Allah, Glorified and Exalted, continually afflicts him with things and trials that he dislikes, until He brings him to that lofty rank."
Abu Ya'la reported it in his Musnad through the chain of Uqbah bin Mukram from Yunus, and Ibn Hibban declared this hadith sahih.

It is narrated from Sa'id bin al-Musayyib (may Allah have mercy on him) that the Messenger of Allah (peace and blessings be upon him) said: "There is no Muslim who is struck by a calamity, and then, even after a long period of forty years has passed, remembers that trial of his and renews the istirja' over it by saying 'Inna lillahi wa inna ilayhi raji'un' (We belong to Allah and to Him we return), except that Allah, Lord of Might, gives him on that occasion the same reward as was granted to him on the day the calamity befell him."
Al-Harith bin Abi Usamah reported this narration in his Musnad. Its chain contains Hisham bin Ziyad and Ali bin Zayd bin Jud'an, who are weak narrators.

It is narrated from the father of Ibn Ajlan: Sayyiduna Abu Hurayrah (may Allah be pleased with him) came to me when I was ill and overcome (by weakness and illness). He asked: "Has this companion of yours prayed?" The people said: "Yes." At this he said: "Know that I have been informed that there is no servant who falls ill except that Allah, the Blessed and Exalted, keeps recording for him (as reward) all the good deeds he used to do in his state of health and well-being, until Allah, the Mighty and Majestic, takes his soul or cures him of the illness and restores him to health."
Ibn Hajar al-Asqalani recorded it in al-Matalib al-'Aliyah, and supporting reports for it exist in Sahih al-Bukhari.

It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "There is no servant who falls into any illness except that Allah Almighty commands the two angels appointed to guard him not to record any evil he does (during that illness), and to record any good he does as equal to ten good deeds, and also to keep recording for him the good deeds he used to do in his state of health and well-being, even if he did not actually do that deed at the time (because of the illness)."
The chain of this report contains Abd al-A'la bin Abi al-Musawir, a liar and matruk (abandoned) narrator, because of whom this chain is severely weak; however, the theme of receiving the reward of one's routine deeds of health during illness is established by other sahih hadith (e.g. Sahih al-Bukhari: 2996).