If you give your money away, do the right good works, and have enough faith then you too can have wealth, health, and prosperity! NOT!! Nothing could be further from Scripture, and if someone tells you otherwise you can be assured that they are a wolf in designer sheep’s clothing. Following Christ results in suffering; believers simply have the ability and responsibility to joyfully use their suffering for the glory of God!
Paul had been chased out of town, beaten, rejected, and imprisoned because he dared to follow God and share the gospel of Jesus. He rejoiced because he suffered so that others would be strengthened in their faith, and his suffering allowed him to identify with Jesus. Verse 24 does not mean that Jesus’ suffering was not enough. Instead it indicates that believers continue to experience some of the suffering that Christ experienced. The world hated Jesus, and now that he is not bodily here to persecute the world will persecute his followers. Suffering allows believers to identify with Christ like nothing else can. As Paul wrote in Philippians 3:10, “I want to know Christ and the power of his resurrection and the fellowship of sharing in his sufferings, becoming like him in his death.” Paul knew that God had given him a commission to proclaim the gospel, and suffering was a part of that.
The phrase “that which is lacking” seems unusual and may have been a catchphrase of these pre-Gnostic false teachers. Remember that they sought to gain special and secret divine knowledge beyond the teachings of the gospel. This phrase does not mean that believers should physically suffer to become closer to God, pressing nails into their flesh, whipping themselves, or crawling on their knees until the flesh is gone as some do. It does not mean that suffering or good works on our part can bring about our salvation or free others from purgatory. This is erroneous doctrine taken from this verse that does not mesh with the rest of Scripture.
Most people are visual and experiential learners. Unbelievers are more likely to be moved by watching a believer’s faith in a trial than by reading an account of the crucifixion. As John Piper put it, “God intends for the afflictions of Christ to be presented to the world through the afflictions of his people. God really means for the body of Christ, the church, to experience some of the suffering he experienced so that when we offer the Christ of the cross to people, they see the Christ of the cross in us. We are to make the afflictions of Christ real for people by the afflictions we experience in offering him to them, and living the life of love he lived.” A watching world will take notice when we respond in love to those who show us hate, when we have hope for the future in face of devastating news and life circumstances, and when we do not worry about tomorrow.
More than that, I count all things to be loss in view of the surpassing value of knowing Christ Jesus my Lord, for whom I have suffered the loss of all things, and count them but rubbish so that I may gain Christ, and may be found in Him, not having a righteousness of my own derived from the Law, but that which is through faith in Christ, the righteousness which comes from God on the basis of faith, that I may know Him and the power of His resurrection and the fellowship of His sufferings, being conformed to His death; in order that I may attain to the resurrection from the dead... I press on toward the goal for the prize of the upward call of God in Christ Jesus. - Philippians 3:8-11, 14