John Calvin Commentary Acts 22:4

"and I persecuted this Way unto the death, binding and delivering into prisons both men and women." — Acts 22:4 (ASV)

I persecuted this way. This is the second point: he was an enemy to Christ’s doctrine and was more fervent in resisting it than all the rest, until he was pulled back by the hand of God. He says the chief priests and elders can testify to this. Therefore, there can be no suspicion regarding such a sudden change.

When he says that he had letters given to him to deliver to the brethren, the term 'brethren' must be understood as referring to the Jews, as though he were calling them his countrymen; but he intended to appease them with this more honorable title. For Paul’s aim here is to declare his natural and legitimate origin from that nation, and also how much he desired to be linked with them in friendship.