Context is important at both ends of contextualization. We must not only look at the context of the culture to which we want to bring the message of the Gospel. We also need to look at the context of the message that we are proclaiming, the context of Scripture.
Now I would remind you, brothers, of the gospel I preached to you, which you received, in which you stand, and by which you are saved, if you hold fast to the word I preached to you – unless you believed in vain. For I delivered to you as of first importance what I also received: that Christ died for our sins in accordance with the Scriptures, that he was buried, that he was raised on the third day in accordance with the Scriptures. 1 Corinthians 15:1-4 ESV
When Paul describes his flexibility, he includes a qualifier. When he says he becomes as one under the law (1 Cor. 9:20) he qualifies it with “(though not being myself under the law)” (ESV). In Galatians 2:11-21, Paul makes it clear that being under the law resulted in conduct that was “not in step with the truth of the gospel” (Gal 2:14). And when he says he becomes as one outside the law he qualifies it with “(not being outside the law of God but under the law of Christ) (ESV).” Paul must be using “law” in two different senses in these qualifiers; the first probably is a reference to the Mosaic code. Carson sheds light on the second sense, being “under the law of Christ,”
The expression is a peculiar one, but the heart of the idea is clear enough. All of God’s demands upon him is mediated through Christ. Whatever God demands of him as a new-covenant believer, a Christian, binds him; he cannot step outside those constraints. There is a rigid limit to his flexibility as he seeks to win the lost from different cultural and religious groups: he must not do anything that is forbidden to the Christian, and he must do everything mandated of the Christian. He is not free from God’s law; he is under Christ’s law. (Carson, p.119, 120)
So there are important limitations in the context that must be kept in mind as we seek to be all things to all men. This flexibility is an expression of Christian freedom to serve others aimed at winning them to the gospel under the law of Christ. We shouldn’t be surprised that our contextualization is constrained by the law of Christ. Part of the Great Commission is to teach the disciples we are making from all nations to observe all that Christ commanded (Matthew 28:18-20).