"So that your faith might not rest in the wisdom of men but in the power of God." (1 Corinthians 2:5)
Weakness and infirmity in the body reveals the fallen state of man. Our Lord Jesus demonstrated the power of God that can come upon sick bodies. He healed people. We read in the Gospels about the stories of healing and even the resurrection from the dead, which established the fact that Jesus is the Son of God. The fact remains that immortality exists only when we get to heavens. Our bodies sown in weakness will be raised up in power. St. Paul states here that when He ministered in Corinth, it was not going well with him. He had his own weaknesses and ailments in his body. He was among them in weakness, fear and trembling. In all probability, he was weak because of a physical ailment . He had mental fears and also moments of discouragement. Yet from such a vessel, God did His work. A church was planted. When the weak Paul preached and ministered, healings took place.
As students of the scripture we should always trust in the sovereignty of God. He knows it all. He knows how best He can use us. He can use us when we are strong and He can use us when we are weak. The message will reach the people irrespective of the condition of the vessel and He displays His glory through sufferings and weakness. We should preach the gospel no matter what our condition is. We should preach and trust in His healing so that the power of the cross might be displayed. He chooses to heal a vessel or He chooses to display His glory and strength in a weak vessel. St. Paul didn't depend on his human wisdom, eloquence, smartness or ability. He chose to just trust in God so that the faith of people would not rest in the wisdom of man but in the power of God!
For further reading: Isaiah 53:1-5, 2 Corinthians 12:9