What does 1 Corinthians 9:27 mean?

Paul has been describing his life of self-sacrifice to win others to faith in Christ using the metaphor of competition. He has compared himself to an athlete who practices self-control in training in order to win the race. Paul's race leads to a prize, as well, the crown of Christ's recognition for his faithful efforts.

Now Paul says this is why he is able to stay motivated. He practices self-control in much the same way as an athlete in training continues to discipline his body with strict self-control over diet, exercise, sleep, and other behaviors. The Greek term Paul uses for "discipline" here is hypōpiazō, which literally refers to beating something black-and-blue. In common use, it implies giving someone a black eye! Paul says he "beats up" his body, like a boxer, to toughen himself for the sake of his spiritual stamina.

Paul remains in this state of continual training because he does not want to be disqualified. He is not talking about losing his salvation as a result of sin. Paul's own teaching is very clear that salvation is a gift, not something that comes as a result of strenuous effort (Ephesians 2:8–9). The prize he is running for is the crown of recognition from Christ that he has served well. In his case, this will include the lives of all of those who have believed in Jesus as a result of his preaching. The context is Paul failing to obtain his goal of winning others, not somehow earning salvation.

Paul recognizes that it is possible for even him to be disqualified of his prize. The runner in a race is disqualified for running off the course, either intentionally or through ignorance. The boxer is disqualified for violating the rules, as well. Paul understands it is not guaranteed that he will finish well. He is not assured of a successful ministry. Nor is he promised to be effective in witnessing to others.

Given what Paul writes in the following chapters, he likely has in mind not just the loss of a crown in eternity. He probably has in mind the Lord's discipline in life for Christians who engage in sinful behaviors. He wrote in chapter 5 about discipline for someone flaunting his sexual sin. He will soon describe God's discipline of His people in the past and the present.