Philippians 3:5

Circumcision of the flesh was one thing that the Judaizers trusted in for acceptance by God. Paul had been circumcised on the eighth day after his birth, as the Law of Moses prescribed (Leviticus 12:3; cf. Genesis 17:12). He had not received circumcision in his thirteenth year, as Ishmaelites did, nor later in life, as many Gentiles did who converted to Judaism (e.g., Acts 16:3). [Note: Robertson, 4:452.]

Second, Paul was an Israelite by birth, not a Gentile proselyte to Judaism. He was a pure Jew by race and descent. When the Jews wanted to stress their special relationship to God in its most unique sense, they used the word "Israelite" to describe themselves. [Note: Barclay, p. 72.]

Furthermore, third, he was a member of the tribe of Benjamin. Benjamin was the younger of the two sons born to Jacob’s favorite wife, Rachel. Benjamin was the only son of Jacob who was born in the Promised Land. The tribe of Benjamin provided many noble warriors throughout Israel’s history (cf. Hosea 5:8). Israel’s first lawful king came from the tribe of Benjamin. Jerusalem and the temple stood within Benjamin’s territory. This tribe alone, beside Judah, remained loyal to David’s house when the monarchy divided in 931 B.C. The feast of Purim celebrated the salvation of the Jews by a Benjamite, Mordecai. After the Exile, Benjamin and Judah formed the core of the restoration community. Of course, this tribe’s history was not without its shame as well (e.g., Saul’s failures, the Gibeans’ atrocity that led to the civil war that almost wiped this tribe out, etc.). Nevertheless Paul could legitimately take pride in his Benjamite heritage.

Fourth, a "Hebrew of Hebrews" means that Paul’s parents brought him up as a strict Jew observing Jewish customs, unlike many Hellenistic Jews (cf. Acts 6:1). Specifically he learned the Hebrew language and studied the Old Testament in the original tongue, not like so many other Jews of the Diaspora who could only speak and read Aramaic (cf. Acts 22:2).

Fifth, Paul had chosen to join the party of the Pharisees, the most orthodox of the sects within Judaism in his day. The Pharisees were punctilious in their observance of the Mosaic Law. This, by the way, is the only occurrence of the word "Pharisee" outside the Gospels and Acts.

"Not content merely to obey the Law of Moses, the Pharisees bound themselves also to observe every one of the myriad of commandments contained in the oral Law, the interpretive traditions of the Scribes. The most ardent of the Pharisees scrupulously avoided even accidental violations of the Law and did more than they were commanded to do . . . . Paul, a son of Pharisees (Acts 23:6), and a disciple of the great Pharisee, Gamaliel (Acts 5:34; Acts 22:3), chose to be a Pharisee himself and set himself to be the most earnest of the earnest observers of the Jewish Law (Galatians 1:14). ’Pharisee’ for Paul was not a term of reproach, but a title of honor, a claim to ’the highest degree of faithfulness and sincerity in the fulfilment [sic] of duty to God as prescribed by the divine Torah’ (Beare)." [Note: Hawthorne, pp. 133-34.]