Originally posted by Salaam_Erin

Paul didn't change the Mosaic Law.  The key to understanding Paul's thinking lies in 3 areas.  One, the Torah and the Hebrew Bible generally say that salvation is by faith.  It does say that if anyone obeys the Torah they will live, but nobody can do that is they  are not righteous, so the sacrificial system for sin was brought in to deal with that.  So Paul cites Genesis 15:6 where Abraham believing the LORD as credited to him as righteousness, the just shall live by faith, that's from Habakkuk 2:4, and Joel 2:32 "He who calls upon the name of the LORD shall be saved."  So while obeying the Torah is important, it cannot save.  Faith and God's mercy saves. 

Two, Paul was mostly writing to Gentiles.  Peter was the first to lead a Gentile to faith in Jesus, namely Cornelius the Roman centurion.  The question emerged, did the Gentile believers need to be converted to Judaism and be circumcised?  Many Jewish believers in Jesus said that they did, which is weird as Jesus never taught this but praised the faith of those Gentiles who trusted in Him.  Paul gave his answer in Galatians.  The answer being no.  Then the Council of Jerusalem met and in Acts 15 we see Peter saying no, Paul and Barnabas gave a missionary report then James, Jesus' brother, a Pharisee, the man who said if you break one law, you break them all, decreed that Gentiles did not need to convert to Judaism but must not eat food sacrificed to idols, from sexual immorality, the meat of strangled animals, and from eating blood.  James then appointed Paul and Barnabas as the enforcers of this.  James also decreed for Moses has been preached in every city from earliest times and is read in the synagogues on every Sabbath.  (Acts 15:21)

So Jewish believers in Jesus remain Jewish, and Gentile believers in Jesus remain Gentile.

This is what Paul taught.  Read 1 Corinthians 7:18  In verse 19 he actually says that circumcision is nothing and uncircumcision is nothing.  It's keeping the commandments that counts.  And what we find in the Bible then is that apart from Abraham and Ishmael and their servants from the very beginning of circumcision, circumcision is for Hebrews/Israelites/Jes (funny thing is, Ishmael, son of Abraham, father of the Arabs, counts as a Hebrew, but not as an Israelite), and circumcision is NOT for Gentiles.  The Old Covenant, superseded but not abolished, is to do with the Land of Israel, and the Israelites, and circumcision is in it, as with the covenant of Abraham.  But the Gentiles post-Abraham are NOT to be circumcised.  Gentiles are not physically descended from Abraham and the New covenant alone is relevant to them, not the older covenants.  However, Paul teaches that the Torah points to Jesus who is the end, the telos, the destination of the Law.  The part of the torah which is abolished, or rather brought to a climax, is the sacrificial system, as Jesus is the final sacrifice.  The Passover Lamb, Paul taught. (1 Corinthians 5:7-8)  This shows that the Passover was still celebrated, but now done every time the Church met and not just once a year, with the Lord's Supper slotted in, as Jesus did (see 1 Corinthians 11), and opened out for Gentiles to partake and not need circumcision and conversion to Mosaic Yahwism/Judaism as before.   The New Covenant, cited by an earlier contributor on this thread is relevant, as it is a covenant NOT like the one God gave to the Israelites when they came out of Egypt, for the Israelites could not keep that covenant.   So God will take that New Covenant, that different Covenant, and place it in their hearts.  Moses spoke in Deuteronomy of the Israelites needing God to circumcise their hearts, Paul takes up this concept.  The key to understanding Paul's nuanced view of the Law is to understand that he sees the Torah as a paedagogos to lead us to Christ, that it is spiritual (Romans 7) but we are sinners needing rescuing by Christ.  Also, we are under a curse of the Law because of our sin.  One, God cursed the ground when Adam and Eve sinned, that's for Gentiles as well as Israelites, while curses were also imposed on the Israelites in the Mosaic Covenant for disobedience (carried out by God in 721 BC and 587 BC and AD 70 when He inflicted judgement on Israel and Judah and Judaea in the Roman era; see Deuteronomy 27 and 28).  Jesus' death removed that curse provided we repent of our sin, Paul taught.  The other key is when Paul says "To those not having the law I became like one not having the law (though I am not free from God's law but am under Christ's law).  Pauol understood that the Ten Commandments were under Christ's law.  Jesus said He came to FULFIL the Torah.  Paul understood what that meant.  He says we are saved not by merit, but by God's grace but then are predestined by God to do good works which He has prepared for us.  Ephesians 2:8-10.  The key is to understand what Jesus meant by fulfilling the Torah.  It is clear that in Paul's thinking, Jews remain Jews, Gentiles remain Gentiles, the New Covenant must be accepted by everyone to get into Heaven, Jesus' death covers this, the Torah shows us we are sinners, and what right and wrong is, the old Torah regime is over, but the Torah is a disciplinarian to lead us to Jesus, and is still spiritual and valuable to expose our sin and call on God's mercy and guide us in terms of how we obey God after salvation.  I hope this helps.