1 Corinthians 9:20

To the Jews I became as a Jew, in order to win Jews; to those under the law I became as one under the lawthough not being myself under the lawso that I might win those under the law.

Acts 16:3

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

Acts 21:20-26

And when they heard it, they glorified God. And they said to him, "You see, brother, how many thousands there are among the Jews of those who have believed; they are all zealous for the law,

Acts 17:2-3

And Paul went in, as was his custom, and for three weeks he reasoned with them from the scriptures,

Acts 18:18

After this Paul stayed many days longer, and then took leave of the brethren and sailed for Syria, and with him were Priscilla and Aquila. In Cenchrea he had his hair cut, for he had taken a vow.

Romans 3:19

Now we know that whatever the law says, it says to those who are under the law, so that every mouth may be stopped and the whole world may be held accountable to God.

Romans 6:14-15

For sin shall not have dominion over you, since you are not under law but under grace.

Romans 11:14

in the hope that I may somehow arouse to jealousy the kinsmen of my flesh and save some of them.

Galatians 4:5

to redeem those who were under the law, so that we might receive 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 accompany him; and he took him and circumcised him because of the Jews who were in those places, for they all knew that his father was a Greek.
Acts 17:2
And Paul went in, as was his custom, and for three weeks he reasoned with them from the scriptures,
Acts 18:18
After this Paul stayed many days longer, and then took leave of the brethren and sailed for Syria, and with him were Priscilla and Aquila. In Cenchrea he had his hair cut, for he had taken a vow.
Acts 21:20
And when they heard it, they glorified God. And they said to him, "You see, brother, how many thousands there are among the Jews of those who have believed; they are all zealous for the law,

Are under

Romans 3:19
Now we know that whatever the law says, it says to those who are under the law, so that every mouth may be stopped and the whole world may be held accountable to God.
Romans 6:14
For sin shall not have dominion over you, since you are not under law but under grace.
Galatians 4:5
to redeem those who were under the law, so that we might receive 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
While he was speaking, a Pharisee asked him to dine with him; so he went in and sat at table.
Romans 15:2
Let each of us please his neighbor for his good, to build him up.
1 Corinthians 10:33
just as I try to please all men in everything I do, not seeking my own advantage, but that of many, that they may be saved.
Galatians 2:3
But even Titus, who was with me, was not compelled to be circumcised, though he was a Greek.