What does Acts 22:3 mean?

Paul is in Jerusalem, facing two different rumors that he is breaking the Mosaic law. He's presently trying to explain to a mob of Jews in Jerusalem why he was seen in Jerusalem in the presence of a Gentile. He starts by quickly covering his background, including his extreme devotion to the Mosaic law.

Tarsus was a Roman city in the province of Cilicia which spans the eastern part of the southern coast of modern-day Turkey. Those who were born in Roman cities such as Tarsus were automatically Roman citizens.

Gamaliel was a famous rabbi of the Pharisees. It was he who counseled the Sanhedrin to ignore the apostles during the very early days of the church, saying, "So in the present case I tell you, keep away from these men and let them alone, for if this plan or this undertaking is of man, it will fail; but if it is of God, you will not be able to overthrow them. You might even be found opposing God!" (Acts 5:38–39).

When Paul says he was "zealous for God," he doesn't mean he was part of the political party now known as the "Zealots." The Zealots were Jewish extremists who approved of violence to drive Romans out of their ancestral lands. Paul trained to be a Pharisee, a religious sect that followed and taught extra-biblical laws for fear of coming close to breaking the Mosaic law. Paul has been accused of teaching Jews they do not need to circumcise their sons and of bringing a Gentile into the temple (Acts 21:21, 28). Anyone trained and steeped in Jewish tradition would never do these things, even were they a follower of Christ.

Paul goes on to explain how he first persecuted the church, then turned to follow Jesus. The crowd listens respectfully until he mentions that God commissioned him to teach Gentiles about the Messiah. The crowd flares again at the mention of Gentiles and demands the tribune take Paul away. The young officer, still confused, obliges (Acts 22:22).