The Noble Scholar Shaykh ‘Abdur-Razzāq Al-Badr حفظه الله stated:

“Sickness as it relates to the believer is a mercy (from Allāh) because it purifies him, removes his sins and expiates his errors. Therefore, it is from Allāh wanting good for him.”

[Sharh Kitāb At-Tibb An-Nabawī]