We have seen something concerning the matter of sickness in a general way. Now we want to pay particular attention to the source of the believers’ sicknesses.
The apostle said, "Because of this many among you are weak and sick, and a number sleep. But if we discerned ourselves, we would not be judged. But being judged by the Lord, we are disciplined that we may not be condemned with the world" (1 Cor. 11:30-32). The apostle considered sickness as a kind of chastisement from the Lord. Because believers have made some mistakes before the Lord, the Lord allows them to become sick. This is for the purpose of chastising them so that they would judge themselves and correct their mistakes. God is gracious to His children by chastising them so that they will not be condemned with the world. If the believers repent, God will not chastise them again. If we are willing to judge ourselves, we will avoid sickness.
We often think that sickness is only a problem of the body and that it has nothing to do with God’s righteousness, holiness, and judgment. But the apostle tells us most vividly that sickness is the result of our sin and that it is a chastisement from God. Because of the story of the blind man in John 9, many believers do not consider that sickness is a chastisement from God because of sin. They do not realize that the Lord Jesus never said that sin and sickness were unrelated. He was merely warning His disciples not to use sin to blame each and every person who was sick. If Adam had not sinned, that man would not have been blind. Furthermore, he was "born" blind; therefore, his case is completely different from that of the believers’ sicknesses. Perhaps all our "born" sicknesses have nothing to do with our sin. But the sicknesses that we incur after we have believed in the Lord, according to the Bible, are related to sin. James 5:16 says, "Confess your sins to one another and pray for one another that you may be healed." One has to confess his sins before he can receive healing. Sin is the root of sickness.
Hence, sickness is usually God’s disciplining so that we would pay attention to the sin that we have neglected and repudiate it. God allows sicknesses to come upon us in order to chastise us and cleanse us, so that we may see our mistakes. Perhaps we have some unrighteousness in us and owe someone something. Perhaps we have offended someone and not corrected it. Perhaps we have pride and a love for the world. Perhaps we have harbored a presumptuous and covetous heart in the work, or have become disobedient after God has spoken. When these happen, God’s hand comes heavily on us to make us pay attention to them. Hence, sickness is God’s clear judgment on sin. This does not mean that whoever becomes sick have sinned more than others (cf. Luke 13:2). On the contrary, those who are chastised by God are mainly the most holy ones. Job is one example.
Every time a believer is disciplined by God and becomes sick, there is the potential of receiving great blessings. "The Father of spirits...discipline[s]...for what is profitable that we might partake of His holiness" (Heb. 12:9-10). Sometimes sickness makes us recall and examine our life; it makes us aware of any hidden sin and any indomitableness and self-will that would cause God to discipline us. Only during such a time will we see what kind of barrier there is between Him and us. Only then will we search the deepest part of our heart and realize how much our past life has been filled with self and how much is incompatible with God’s holy life. In this way, we will be able to advance in the spiritual life and receive God’s healing.
(Spiritual Man, The (3 volume set), Chapter 40, by Watchman Nee)