Al-Matalib al-'Aliyah 2460 — Illness as expiation, the reward

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).