"Do you not know that in a race all the runners compete but only one receives the prize? Then so run that you may receive But everyone that contends trains himself. They do it to receive a perishable crown but we an imperishable. Therefore I so run, not uncertainly. I do not fight as one beating the air but I pommel my body and bring it into subjection lest after preaching to others I myself should be reprobated."
Reprobated? Did we hear Paul right? Reprobated? Yes, this is the very same Greek word that is used at Romans 1:28, 2 Corinthians 13:5, 2 Corinthians 13:6, 2 Timothy 3:8, Titus 1:16 and Hebrews 6:8 which are all the other occurrences of this word in the New Testament. In these passages the word is commonly translated as "reprobate" in major translations. The word means "to reject" or "to be rejected," "unapproved" or "unfit."
Here Paul is telling us that he brings himself into subservient subjection lest he be reprobated from the prize. What is the prize exactly? This word is used in one other place in the New Testament"That I may know him and the power of his resurrection and the fellowship of his sufferings, becoming like him in death, so that somehow I might obtain the resurrection of the dead. Not that I have already obtained this or already been made perfect, but I press on to make it my own because Christ Jesus has made me his own. I press on toward the mark of the prize of the calling above of God in Christ Jesus.... our citizenship is in heaven from where we await a Savior, the Lord Jesus Christ who will change our humble body and transform it to be like his glorious body by the power which enables him to subject all things to himself." (Philippians 3:10-21)
Here we see Paul telling us that his goal is the resurrection of the dead. This is the prize to which we are called above, the glorification of the body. This is the incorruptible crown for which we strive. The words "corruptible" and "incorruptible" are the language Paul uses to refer to the resurrection of the body. Peter also uses this terminology to refer to our salvation reserved in heaven for us (1 Peter 1:4-5).
And even further Paul goes on in the verses (10:1-12) which follow to warn Christians that they will be condemned if they follow the same example of the Israelites in the wilderness. Here, Paul tells the Corinthians that he brings his body under subjection to God so that he is not disqualified for the eternal prize. And then he follows this up by instruction the Corinthian Christians not to fall short of salvation on the last day by becoming unfaithful to God.
Paul is telling us that he knows there is a prospect of not being saved at the end of the age. And this is precisely why he gives us this exhortation in this passage. Paul feared reprobation if he did not remain true to Christ. So should we.