Is sickness ever part of God's will for believers?

from the old testament

• Although God allowed Adam and Eve to make the choice that enslaved humanity to sin, it was not God's will for humanity to sin—He is perfectly holy, His very nature being in exact opposition to sin (Psalm 5:4; 92:15; see also James 1:13). It is also not God's will for us to live forever with the consequences of sin.
• In most cases, illness and death are a natural outcome of the general entrance of sin into the world (Genesis 3). Sin introduced death and all manner of associated brokenness, including sickness. However, there have been rare occurrences when God has directly inflicted an illness upon someone to teach a lesson or in cases of grave sin (Daniel 4:28–37; 2 Chronicles 26:19–20).

from the new testament

• When Adam and Eve gave in to Satan's temptation in the garden of Eden, they brought both sin and evil into a formerly perfect world. The result of sin is death (Romans 6:23).
• All of creation, including humanity, has been suffering under death's curse ever since (Romans 5:12; 8:19–22). Death encompasses both physical and spiritual death and means more than our hearts ceasing to function or spending eternity in hell. Among other things, death also includes the natural evils of our world—evils like sickness and disease. Despite the fact that sin and evil, with all their consequences, have taken hold of mankind, there is nothing that happens without God's allowance.
• The New Testament reveals a few occurrences when God directly inflicted death or illness leading to death in the case of egregious sin (Acts 5:1–10; 12:20–23).
• Even though illness and sickness exists, Jesus also proved that He is sovereign over even disease by performing miracles where He healed people. In Matthew 8:16-17, Jesus healed all who were brought to Him. Mark 1:32-34 describes Jesus healing many sick with various diseases and casting out demons. In Luke 7:21-22, Jesus healed those with diseases, plagues, and evil spirits and told John’s disciples to report these signs as proof of His messianic identity.
• God may also use sickness as a means of loving discipline for believers (Hebrews 12:5–11).
• James 5:13–15 counsels, “Is anyone among you suffering? Let him pray. Is anyone cheerful? Let him sing praise. Is anyone among you sick? Let him call for the elders of the church, and let them pray over him, anointing him with oil in the name of the Lord. And the prayer of faith will save the one who is sick, and the Lord will raise him up. And if he has committed sins, he will be forgiven.” Sickness may or may not be linked to sin in such a situation, and it is always something about which we can pray. It is not wrong to seek physical healing and support for sickness. In fact, such healing is something for which we can give gratitude to God, knowing that He alone is ultimately our Healer, by whatever means He might provide.
• No matter the cause of a particular illness, God can use it for our good and His glory (Romans 8:28). We can cast our worries on Him, trusting in His care (1 Peter 5:6–11). We can also trust that any trials we endure can lead to spiritual growth (James 1:2–4; 1 Peter 1:6–9).
• Not only has He provided Jesus as our Savior, one day God will create "a new heaven and a new earth" (Revelation 21:1) without the stain of sin. Though sickness might be part of God’s permissive will now, and even something He specifically uses for a variety of purposes, sickness will not be an eternal reality. We can trust that He is sovereign now and rely on His steadfast love. We can be encouraged by Paul’s word, “So we do not lose heart. Though our outer self is wasting away, our inner self is being renewed day by day. For this light momentary affliction is preparing for us an eternal weight of glory beyond all comparison, as we look not to the things that are seen but to the things that are unseen. For the things that are seen are transient, but the things that are unseen are eternal” (2 Corinthians 4:16–18).

implications for today

Regardless of whether God actively inflicts an illness or passively allows it, we can see His ultimate purposes: to bring glory to Himself and to reveal His nature to us. God's power and sovereignty allow Him to use even the direst of circumstances to bring about His sovereign will. This may include showing His power through miraculous healing (John 9:1–3), bringing non-believers to salvation, or any number of things—including those known only to Himself.

Make no mistake—God is grieved when those He loves are suffering. He often shows His love and compassion for us through others who minister to us and care for us during times of sickness (2 Corinthians 1:3–5). And no matter what happens, we can trust that God is good, because that is His nature. He will never unnecessarily afflict us, and He can use these times of sorrow to bring about good things in our lives or the lives of others (Romans 8:28–30).

Even though it can be difficult to experience illness or to watch those we love suffer, we can still have faith that God is sovereign and that He cares for each one of us. We may not see His plans and purposes come to fruition during our lifetimes, but we can rest assured that God knows what He is doing.