Paul is one of the most important apostles in the New Testament era. He wrote a significant portion of the New Testament and is called the Apostle to the Gentiles for his vigorous evangelism to non-Jews.

Life
A Pharisee belonging to the tribe of Benjamin, he was from Tarsus in Cilicia and was educated in the law under Gamaliel (Rabbi).
Phil 3:5circumcised on the eighth day, of the nation of Israel, of the tribe of Benjamin, a Hebrew of Hebrews; as to the law, a Pharisee;Phil 3:6as to zeal, a persecutor of the church; as to righteousness under the law, blameless.
He was zealous for the law.
Gal 1:14and I was advancing in Judaism beyond many of my contemporaries among my own people, so extremely zealous was I for the traditions of my fathers.
He had Roman citizenship from birth.
Acts 22:26When the centurion heard this, he went to the tribune and said, “What are you about to do? For this man is a Roman citizen.”Acts 22:27So the tribune came and said to Paul, “Tell me, are you a Roman citizen?” And he said, “Yes.”Acts 22:28The tribune answered, “With a large sum I obtained this citizenship.” Paul said, “But I am a citizen by birth.”
From this, it can be inferred that although he was born into an orthodox Jewish family, he came from a very influential family and was extremely zealous for the law.
Because he held these values, he believed that Christians treated the law lightly and desecrated the temple.
Therefore, when Deacon Stephen was killed and persecution arose, he participated,
Acts 8:1And there arose on that day a great persecution against the church in Jerusalem, and they were all scattered throughout the regions of Judea and Samaria, except the apostles.Acts 8:2Devout men buried Stephen and made great lamentation over him.Acts 8:3But Saul was ravaging the church, and entering house after house, he dragged off men and women and committed them to prison.
Furthermore, on his way to Damascus to actively persecute Christians, he met Jesus and dramatically converted.
Acts 9:1But Saul, still breathing threats and murder against the disciples of the Lord, went to the high priestActs 9:2and asked him for letters to the synagogues at Damascus, so that if he found any belonging to the Way, men or women, he might bring them bound to Jerusalem.
Afterward, he actively embarked on missionary journeys to Asia Minor and Europe, writing numerous scriptures.
Paul's Missionary Journeys
First Missionary Journey