The reason that God has established a covenant of peace (Romans 5:10) with man is because it is the goodness of God that draws man to God through repentance (Romans 2:4). So many times we think that God is using His wrath and judgment to teach us lessons that will make us turn to Him, but it is clear in the Book of Revelations that wrath turns man away from God. This inaccurate belief of God using sickness, disease, poverty, death, or anything else that is not founded in peace or love does not make sense if you compare it to the living example of Jesus Christ.
John 13:15 (KJV): For I have given you an example, that ye should do as I have done to you.
Now since Jesus came as an example, He has done everything that He has told us to do. So to the people who believe that God uses sickness, disease, death, accidents, etc. to teach us lessons, I would ask them to show me one place in the Bible where Jesus used these same means to teach lessons? In fact, show me one place in the Bible where Jesus left an individual worse off than where He found them? You will not find such an example because this perverse sense of teaching is not in the nature of God. And to show this scripturally we will look to Hebrews:
Hebrews 1:3 (KJV): Who being the brightness of His glory, and the express image of His person, and upholding all things by the Word of His power, when He had by Himself purged our sins, sat down on the right hand of the Majesty on High.
Hebrews 1:3 is speaking about Jesus being the express image of God. The phrase “the express image” in Greek is “charaktēr” (χαρακτήρ), and means “the exact expression (the image) of any person or thing, marked likeness, precise reproduction in every aspect”. Jesus is the exact image of God the Father, and He never used any test, sickness, disease, accident, poverty, or calamity to teach His children lessons. He used love through His goodness to draw people to Him. This is the nature and character of our loving God.
In fact, this idea is so illogical that if God used cancer to teach people lessons, I could never witness to them and pray for healing because it would oppose the will of God. If God took children away from parents, I could never witness to any parent and bring them to Christ. If God used natural disaster to judge cities and kill people, why would we send aide and resources to help them out when it is the will of God that they suffer? In fact, if God killed ANYBODY I could not witness to a single sole and try to bring them to a God that might kill them one day.
This is idea of God using sickness and disease is not consistent with the loving nature of God. He loves you. He sent His son to die on the cross that you would have life, fulfillment, joy, and healing. Quite the opposite of what some of us can believe.
Psalm 107:20: And He sent His Word and healed them, and delivered them from their destructions.