The New Testament records Paul's conversion and ministry across Acts, and thirteen epistles are traditionally attributed to him — from Romans through Philemon.
Traditional attribution: Thirteen New Testament epistles are traditionally attributed to Paul (Wikidata Q9200).
Key passages:
"And he fell to the earth, and heard a voice saying unto him, Saul, Saul, why persecutest thou me?" — Acts 9:4
"But the Lord said unto him, Go thy way: for he is a chosen vessel unto me, to bear my name before the Gentiles, and kings, and the children of Israel:" — Acts 9:15
"For I am the least of the apostles, that am not meet to be called an apostle, because I persecuted the church of God." — 1 Corinthians 15:9
"Paul, an apostle, (not of men, neither by man, but by Jesus Christ, and God the Father, who raised him from the dead;)" — Galatians 1:1
Read the account of his conversion in Acts 9:1-22 and his own words in Romans and the Pauline epistles.