For the pre-Christian Paul, Jesus was a heretical teacher, a false messiah, who undermined the very basis of Judaism.
Formation And Struggles: The Birth of the Church AD 33-200, by Veselin Kesich
As a Christian missionary, Paul was the most influential leader in the first-century church.
His letters are historical and spiritual; they are sources for the organization of church life and worship; they offer meaningful theological development. While he was a contemporary of Jesus, there is no indication that he ever met Jesus before Christ’s ascension.
Paul was born in Tarsus around 6 BC, a place of a well-established Jewish diaspora. In Tarsus, he received both a Jewish and Hellenistic education. He would commit many passages of the Hebrew Septuagint to memory, later quoting Scripture extensively for exhortation and teaching. It is estimated that his epistles contain about ninety explicit quotations from Scripture in addition to numerous allusions.
He also likely read Homer, a must in the Hellenistic world. There is evidence that even in Pharisaic Jerusalem that Homer was read. All in all, Paul was at home in two different cultures, in two different languages. And he was a Roman citizen.....
Conclusion
Paul’s epistles are our primary source, aside from the book of Acts, for the mission and expansion of the church from approximately the 40s to the Jewish-Roman War (AD 68-70).
Through his preaching, teaching, and letters, he would challenge both Jews and Gentiles in this Christian faith. In the face of Hellenistic cults and practices, in the face of orthodox Judaism, he would stand against any type of blending of religious beliefs and practices.
1 Corinthians 1: 18 For the message of the cross is foolishness to those who are perishing, but to us who are being saved it is the power of God. 19 For it is written:
“I will destroy the wisdom of the wise,
And bring to nothing the understanding of the prudent.”