He meant when he wrote, Philippians 3:4-8, RSVCE"Though I myself have reason for confidence in the flesh also. If any other man thinks he has reason for confidence in the flesh, I have more: circumcised on the eighth day, of the people of Israel, of the tribe of Benjamin, a Hebrew born of Hebrews; as to the law a Pharisee, as to zeal a persecutor of the church, as to righteousness under the law blameless. But whatever gain I had, I counted as loss for the sake of Christ. Indeed I count everything as loss because of the surpassing worth of knowing Christ Jesus my Lord. For his sake I have suffered the loss of all things, and count them as refuse, in order that I may gain Christ."
Galatians 1:13, RSVCE "For you have heard of my former life in Judaism."
Former life as in legalism and persecutor of those who believed in Messiah before the LORD called him.
Gen 1: 1- 2; Ge 6:3; Isa 43:11; Isa 44:6; Isa 45:5; Isa 63:10,11; Ezek 1:13-21; 10:2-7; Dan 7:9,10, 13, 22; John 1:1-4, 10-14; John 15 - 17; Philippians 2:5-11; Col 1:12-20; Rev 1:11-18