1 Corinthians 9:20

And to the Jews I became as a Jew [not a Jew, but like one], that I might gain Jews [Paul observed the Jewish distinction as to meat (1 Corinthians 8:13); and performed their rites as to vows (Acts 21:26); and honored their feasts (Acts 20:16); and classed himself among their Pharisees (Acts 23:6); and even had circumcision administered (Acts 16:3), where it did not interfere with the liberty of Gentiles (Galatians 2:3-5). All these were innocent concessions to and harmless compliances with the law. Though Paul was under no obligation to conform his conduct to the prejudices of others, he waived his own predeliction in all matters that were indifferent; but his unbending, unyielding loyalty in all matters of principle was so well known that he does not deem it necessary to state that he never surrendered or sacrificed a single truth or right for any cause]; to them that are under the law [This expression includes proselytes as well as Jews. To these also Paul made harmless concessions], as under the law, not being myself under the law, that I might gain them that are under the law;