In 1 Corinthians 9, the Apostle Paul gives an insight into how he approached ministry. After discussing how he related to Jews, gentiles, and those whom society had looked down upon, Paul sums up how he related to each of these groups by saying that he became “all things to all people.”
For the Jewish people, they had the Law. In the early church, there was still some uncertainty over which (if any) aspects of the Law people were required to follow.
Paul was respectful of Jewish customs. He had been born and raised Jewish. And for the sake of building relationships, in certain circles, he would still participate in accordance with various Jewish customs. In Acts 16, Timothy is a young minster who begins doing ministry with Paul. Knowing they would be traveling in heavily Jewish areas, Paul actually has Timothy get circumcised.
All things to all people.