With this phrase, Paul identifies himself as a zealot, in the same category as Simon (Mark 3:18).1 Inspired by the example of Judas Maccabees, Phinehas (Numbers 25:11), and Elijah (1 Kings 19:10, 1 Kings 19:14), zealots sought to ensure that the Mosaic laws and Pharisaic traditions were strictly practised and kept in Israel.
14 And I was advancing in Judaism beyond many of my own age among my people, so extremely zealous was I for the traditions of my fathers.