Al-Matalib al-'Aliyah 2451 — Illness as expiation, the 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.