1CO 9:20

20 Specifically, when I was with fellow Jews, I did the things that Jews [think that people should do]. I did that in order that I might convince some of them [to trust in Christ]. Although I am now not obligated to obey the Jewish laws and rituals, when I was with those who believe that they are obligated to obey those laws, I did the things that they [think that people should do]. I did that in order to convince some of them [to trust in Christ].