A letter to the incarcerated muslim with appendices regarding major sins

If a sick person went to the doctor for treatment and was advised to avoid certain delicious foods to preserve his health, he would believe the doctor and comply with the doctor’s orders. Despite this, we see many people disobeying Allāh and His Messenger by leaving off the obligations while doing prohibited actions; although he reads and hears the commands and prohibitions. He knows the permissible and the impermissible. Therefore, is the doctor more truthful to them than Allāh, the Exalted? Or is their sickness more severe to them than the Hellfire?