Galatians 2:3
But they did not even require that Titus, a Greek [i.e., a Gentile] who was with me, become circumcised.
Acts 16:3
Paul wanted him to travel with him [on a preaching mission] so he had him circumcised in order to avoid prejudice by the Jews in that area, for everyone knew that his father was a Greek.
Acts 15:24
We have heard that certain [men] who left here have been upsetting you people and [even] undermining [some people's] spiritual lives by what they have been teaching. This was done without our authorization [or approval].
1 Corinthians 9:20-21
I behaved like a Jew in front of the Jews in order to win Jews [to Christ]. I behaved like a person who was under [obligation to observe] the law [i.e., Jews] in front of those who observe that law, although I was not [really] under [obligation to] it. I did this to win those who are under [obligation to observe] the law.
2 Corinthians 2:13
I had no peace of mind because I did not find my brother Titus [there]. So, I said "good-bye" to them and went on to Macedonia.
Galatians 5:2-6
Look, I Paul am telling you that, if you revert to [the practice of] circumcision [i.e., the Jewish rite of identity, signifying the responsibility to observe the law of Moses], then Christ's [sacrifice] will be of no value to you.