Jesus and the Apostles were Jews. The Bible has to be understood within the framework God Himself established, not the Greco-Roman one modern man has adopted. He renounced the Pharisees because of their man-made doctrines. He renounced sin, which is self (who has not thought or behaved in a way that says we know better than our Creator?). To be holy is to be separate. Did He not separate the Israelites from the rest of the nations? Did He not separate them further by His laws and commands? Did that separating change when Jesus amended the old pact by His blood baptism? No, we became spiritual Israel (Romans 2:29, Romans 4:16, Romans 8:16, Galatians 3:7, Galatians 4:26, Galatians 6:15-16, Hebrews 12:22-23, Ephesians 2:11-13, Ephesians 2:19-20, Philippians 3:3, Colossians 2:11 ), whom God knew before He created man (Acts 13:48, Romans 8:29-30, 1 Corinthians 2:7, Ephesians 1:3-12, 2 Thessalonians 2:13-14, 2 Timothy 1:9). “Deny yourself, take up your cross, and follow Me.” See Matthew 10:38, Matthew 16:24, Mark 8:34, Mark 10:21, Luke 9:23, Luke 14:27. Isaiah was Israelite who already knew what sexual sin was. That has not and will never change. Through Him (His sacrifice and the indwelling of the Holy Ghost), we have a chance to become sinless. As we die to self and obey Him (doing faith), sin decreases.