1 Corinthians 9:20

To the Jews I became as a Jew, so that I might win Jews; to those who are under the Law, as under the Law though not being myself under the Law, so that I might win those who are under the Law;

Acts 16:3

Paul wanted this man to go with him; and he took him and circumcised him because of the Jews who were in those parts, for they all knew that his father was a Greek.

Acts 21:20-26

And when they heard it they began glorifying God; and they said to him, “You see, brother, how many thousands there are among the Jews of those who have believed, and they are all zealous for the Law;

Acts 17:2-3

And according to Paul’s custom, he went to them, and for three Sabbaths reasoned with them from the Scriptures,

Acts 18:18

Paul, having remained many days longer, took leave of the brethren and put out to sea for Syria, and with him were Priscilla and Aquila. In Cenchrea he had his hair cut, for he was keeping a vow.

Romans 3:19

Now we know that whatever the Law says, it speaks to those who are under the Law, so that every mouth may be closed and all the world may become accountable to God;

Romans 6:14-15

For sin shall not be master over you, for you are not under law but under grace.

Romans 11:14

if somehow I might move to jealousy my fellow countrymen and save some of them.

Galatians 4:5

so that He might redeem those who were under the Law, that we might receive the adoption as sons.

Galatians 4:21

Tell me, you who want to be under law, do you not listen to the law?

Galatians 5:18

But if you are led by the Spirit, you are not under the Law.

Treasury of Scripture Knowledge

Summary

And unto the Jews I became as a Jew, that I might gain the Jews; to them that are under the law, as under the law, that I might gain them that are under the law;

Bible References

Unto

Acts 16:3
Paul wanted this man to go with him; and he took him and circumcised him because of the Jews who were in those parts, for they all knew that his father was a Greek.
Acts 17:2
And according to Paul’s custom, he went to them, and for three Sabbaths reasoned with them from the Scriptures,
Acts 18:18
Paul, having remained many days longer, took leave of the brethren and put out to sea for Syria, and with him were Priscilla and Aquila. In Cenchrea he had his hair cut, for he was keeping a vow.
Acts 21:20
And when they heard it they began glorifying God; and they said to him, “You see, brother, how many thousands there are among the Jews of those who have believed, and they are all zealous for the Law;

Are under

Romans 3:19
Now we know that whatever the Law says, it speaks to those who are under the Law, so that every mouth may be closed and all the world may become accountable to God;
Romans 6:14
For sin shall not be master over you, for you are not under law but under grace.
Galatians 4:5
so that He might redeem those who were under the Law, that we might receive the adoption as sons.
Galatians 5:18
But if you are led by the Spirit, you are not under the Law.

General references

Luke 11:37
Now when He had spoken, a Pharisee *asked Him to have lunch with him; and He went in, and reclined at the table.
Romans 15:2
Each of us is to please his neighbor for his good, to his edification.
1 Corinthians 10:33
just as I also please all men in all things, not seeking my own profit but the profit of the many, so that they may be saved.
Galatians 2:3
But not even Titus, who was with me, though he was a Greek, was compelled to be circumcised.