Let’s go to Colossians, chapter 1, and we’ll look at one verse: verse 24: “Now I rejoice in my sufferings for your sake, and in my flesh I do my share on behalf of his body (which is the church) in filling up that which is lacking in Christ's afflictions.” Paul suffers, and he says that in his sufferings he fills up what is lacking in Christ’s afflictions? What does that mean?
Here’s my answer in summary: What’s missing is the in-person presentation of Christ’s sufferings to the people for whom he died. The afflictions are lacking in the sense that they are not seen and known among the nations. They must be carried by ministers of the gospel. And those ministers of the gospel fill up what is lacking in the afflictions of Christ by extending them to others.
Paul sees his own suffering as the visible reenactment of the sufferings of Christ so that they will see Christ’s love for them.