Note 9 at 1 Cor. 9:21: To the non-religious, Paul didn't act religious. It would have caused them to reject the message because of the messenger. Today our Christian cliches and mannerisms are at best meaningless and sometimes offensive to non believers. Paul would have related to them as much as he could so that he could share the gospel with them. Paul is not advocating becoming like the world, but he is advocating not trying to make the world become like us before they hear the gospel. You have to catch the fish before you clean them.

Note 10 at 1 Cor. 9:21: A New Testament believer is not obligated to fulfill the Old Testament law for justification (see notes 3-4 at Rom. 3:19, p. 757). Therefore, Paul referred in the previous verse to not being under the law. Yet here he says he is under the law to Christ. There are two ways to understand this.

First, a Christian is not under the Old Testament law but under the New Testament law of Christ, which is to love God with all your heart and love others as yourself (Mt. 22:37-39; Mk. 12:30-31; Rom. 13:9-10; 1 Jn. 4:21). If a person walked in this law of Christ perfectly, he would fulfill the righteousness of the Old Testament law. "Love worketh no ill to his neighbour: therefore love is the fulfilling of the law" (Rom. 13:10).

Secondly, a New Testament believer does not discard the Old Testament law, he just ceases to try and fulfill it as a requirement for salvation. This is exactly what the apostle John was referring to in 1 John 2:7-8. In verse seven, John said he wasn't writing a new commandment. It was the same commandment that they had heard from the beginning, referring to the Old Testament scriptures. Then in verse eight, he says it is a new commandment- new in the sense that the holiness the law dictated now comes as a fruit and not a root of salvation.

So, Paul was not wrong to infer in verse 20 that he was not under the jurisdiction of the O.T. law, and he was not wrong in verse 21 to say that he was under the new law of Christ.