In Colossians 1 verse 24 It implies that Christ’s sufferings were insufficient to cover the sins of the body of Christ [the church] and that Paul needed to ‘fill’ up ‘that which is behind’ of the afflictions of Christ. PLEASE explain and thank you for this truly great website.
In Acts 9:16 the Lord said He would show Paul how much he must suffer for His Name. In Colossians 1:24 Paul spoke of how much he rejoiced in those sufferings and how he wanted to experience all that was yet to come of the afflictions of Christ to be borne by him, because of how it would benefit the Church. He wasn’t trying to imply that the Lord’s suffering was anything less than sufficient to pay for our sins.
Had Paul been saying that he had to finish the job Jesus only started, it would have been a contradiction of both the Lord’s last words on the cross (“It is finished”) and of everything Paul taught, because it would have meant Paul thought of himself as a partner with Jesus in providing for our salvation.