Philippians 3:5-6

Furthermore as a Pharisee he had meticulously sought to follow the Law (as interpreted by them), while his zealousness as a Jew had been proved by the way in which he had persecuted those Jews who were considered to have gone astray, the new-born church. And as regards the righteousness of the Law he had been able to tick off every box demonstrating that he had fulfilled all that was required of him by the Rabbis. No finger (apart from God's) could have been pointed at him, because he had been found blameless (by men; compare the rich young ruler's view of himself in Matthew 19:20, and yet he too was still dissatisfied and aware of something missing). We may see this blamelessness in the eyes of men as in contrast with his requirement of the Philippians in Philippians 2:15. They were to seek to be blameless in the eyes of God.

His persecuting of the new-born church would have been seen by his fellow-Pharisees as especially revealing his righteousness. Here was a man who was zealous for the Lord of Hosts. When Phinehas had slain the offending Israelite in Numbers 25:6 it had been ‘accounted to him for righteousness to all generations for evermore' (Psalms 106:30). In Jewish eyes it had established him among ‘the righteous ones'. The same was true of Mattathias, the father of the Maccabees, for he too had slain an apostate Jew in the act of offering a false sacrifice, and his action had been described as being ‘Zealous for the Law' (1Ma 2:24-28). Thus Paul, in persecuting the church, had seen himself as aligning himself with the zeal of his fathers.