“Though I am free and belong to no one, I have made myself a slave to everyone, to win as many as possible” (v19). Paul, a Jew, was no longer “under the law” because he knew Christ had fulfilled the law’s requirements for him, and instead he lived “under Christ’s law” (v21). However, in order to win Jews and Gentiles to Christ, he was willing to adapt to both groups so that the gospel could be clearly communicated (v20-21). His own freedom was secondary.
“I do all this for the sake of the gospel” (v23). The amazing good news that reconciled us to God is meant to be shared with everyone, even at the cost of our own comfort.