In 2 Corinthians 11:23-33, Paul speaks about the varied trials that he had experienced in his service for the Lord - his imprisonments, the beatings he had received both with scourges and with rods, sleepless nights, hunger and thirst, exposure to inclement weather, dangers from robbers, etc. There were times when he did not have enough warm clothing to cover himself, or even enough food to eat; and he did not have the money to buy warm clothes and food at that time. God took him through all this to make him a mini-forerunner for other Christians who were suffering. In each of those trials, Paul humbled himself.
He says, "Once I was going to be captured in Damascus and the believers had to lower me in a basket through a window for me to escape capture" (2 Corinthians 11:32, 33). If you were an apostle, and something as humiliating as that had happened to you, you may not want anyone to hear about it. But Paul did not want the Corinthian Christians to imagine that he was a great man whom God would send some angels to rescue. He was an ordinary man and he wanted others to know him as such. "I don't want anyone to think more highly of me than he should", he said (2 Corinthians 12:6 - Living). How different Paul was from most servants of the Lord today who try to give others a higher impression about themselves than they actually are.
In 2 Corinthians 12:1, Paul speaks about a time when he was taken up by the Lord to the third heaven. For 14 years he had never mentioned it to anyone. What a man he was! He had kept quiet about this experience for 14 years - and even when he did speak about it, he gave no details whatsoever. Most believers would have spoken about such a vision in the very next meeting of the church - and given every detail about it! This is why I believe Paul's experience was genuine. The visions of heaven that some believers boast about these days are figments of their fertile imagination - spoken in order to get honour from others! Why do I say that? Because those who have genuine visions will find that those visions are (as Paul said) "so astounding that they are beyond a man's power to describe or put in words" and they will "not be allowed to tell them to others" (2 Corinthians 12:4).
Then Paul spoke about a heavy trial that he had that God did not remove, even after persistent prayer. Paul called it "a thorn in the flesh" and "a messenger of Satan" - yet it had been "given by God" (2 Corinthians 12:7). The gift God gave Paul was a thorn!! God gave it to Paul because He saw Paul in danger of becoming proud. God resists all proud people, but He didn't want to resist Paul. He wanted to give him grace. But He could give Paul grace only if he remained humble (1 Peter 5:5). So God allowed Satan's messenger to harass Paul and thus kept him constantly dependent on God and humble. So we see that, at times, God may permit even a messenger of Satan to keep on harassing us, with a good end in view. Sickness, for example, is a messenger of Satan. Why do we say that? Because Jesus said, "If you, being evil, know how to give good gifts to your children, how much more will your Father in heaven give (only) what is good to those who ask Him" (Matthew 7:11). We are all evil fathers when compared to God, Who is perfectly good. And none of us would ever give sickness to our children. Then how could a loving, heavenly Father give sickness to any of His children? Most of the sicknesses in the world come because the earth is under a curse (Genesis 3:17). Some other sicknesses are caused by Satan (Job 2:7).
Even though God's perfect will for us is to be healthy, He may still permit us to be sick at times, with a purpose. When Paul prayed for deliverance from the thorn, God did not deliver him but gave him grace instead, to be an overcomer in spite of the thorn. We can be overcomers too with that same grace. In 2 Corinthians 13:4 and 5, we read, "Jesus was crucified in weakness, yet He lives by the power of God. We also are weak in Him, yet we will live with Him because of the power of God."
A true disciple is one who is weak in himself and who lives by God's power. And that is how Paul concludes the epistle.