Final answer:
Paul's teacher when he was studying to be a Pharisee was Gamaliel.
Step-by-step explanation:
When Paul was studying to be a Pharisee as a young man, his teacher was Gamaliel.
Gamaliel was a highly respected Jewish scholar and member of the Sanhedrin, the Jewish high council. He is mentioned in the New Testament as a teacher of the Apostle Paul, also known as Saul of Tarsus.
Gamaliel's teachings had a significant impact on Paul's understanding of Jewish law and traditions, as well as his later role as a leader in the early Christian church.