Paul identified himself as being born a Jew but he never said that as a convert to Christianity he was still bound to keep the OT law nor did he command others to keep it. Acts 21 Paul gives account to the Jews as to what God had done among the Gentiles, God used Paul to go to the Gentiles. Those Christian Jews were happy and pleased with what took place among the Gentiles. Verse 20 many Jews had converted to Christianity and it appears some were still keeping the OT law as a matter of custom not out of command,necessity:
Jesus did not come to start his own religion, but rather he practiced Judaism by living in sinless obedience to the Torah, spent his ministry teaching how to obey it by word and by example, and being a follower of Christ is about following what he taught (1 John 2:6, 1 Peter 2:21-22), so Jews who became his followers were not converting to a different religion or ceasing to obey the Torah, but rather they were becoming zealous for it (Acts 21:20). I'm not seeing a good reason for you to assume that becoming a follower of Christ involves refusing to follow him. In Acts 21:20-24, Paul took stepes to disprove false rumors that he was teaching against the Torah and to show that he continued to live in obedience to it. A Pharisees is a Torah observant sect of Judaism of which Paul identified as a member, and in Acts 24:14, he testified that he continued to believe in the God of our fathers, believing everything laid down by the Torah and written in the Prophets.
It does not say that their obedience was a matter of custom and not our of command.
Yet Paul had by this time
(Acts 20) written Romans and Galatians, books that made it clear that Christians-even Christians of a Jewish background were no longer under the Law of Moses (Romans 7:1).
Galatians 3:25 "Now that faith has come, we are no longer under a tutor". And equally, that continued observance of the Law in order to find favor with God (like circumcision, or observing days), would result in falling from grace (Galatians 5:1-4).
In 2 Peter 3:15-17, it says that Paul is difficult to understand, but that those who are ignorant and unstable twist his words to their own destruction and are carried away by the error of lawless men, so even in his day there were people who were misunderstanding passages like the ones you've listed as being against obeying God's law, but we can be confident that when Paul is correctly understood that he never did that. Someone who disregarded everything that their tutor taught them after they left would be missing the whole point of a tutor. All throughout the Bible, God wanted His people to repent and to return to obedience to His law, and even Christ began his ministry with that message, so it would be absurd to interpret Galatians 5:4 as Paul warning us against following Christ and saying that we will be cut off from Christ if we follow Christ. In Psalms 119:29, David wanted God to be gracious to him by teaching him to obey His law, so that is what it means to be under grace, not the way to fall from grace. Paul's problem in Galatians was not with those who were teaching Gentiles how to follow Christ's example of obedience to the Mosaic Law, but with those who were wanting to require Gentiles to obey their works of the law in order to become justified.
One can be zealous for the Law without continuing to observe the obsolete system (as the Hebrew writer calls it, (Hebrews 8:13)
That is, I still view it as the word of God and learn the lessons that it teaches (
Romans 15:4).
In Hebrews 8:10, the New Covenant still involves following God's law, so while the Mosaic Covenant has become obsolete, God's eternal law did not become obsolete along with it. It was sinful to commit adultery in Genesis 39:9 before the Mosaic Covenant was made, during it, and after it has become obsolete, so there is nothing about it being made or becoming obsolete that changes which actions are righteous or sinful. It is worthless to learn lessons that have no practical application for how we should live our lives.
One could continue to observe certain elements in the Law merely from the standpoint of custom. That is, circumcision was still allowed - simply as a surgical practice (1 Corinthians 7:19).
One could still go to Jerusalem during Passover or Pentecost and attend those feasts as one would attend any other national festival. One could go to the Jewish synagogue on the Sabbath in order to teach people, and one could still observe various food laws - simply as a matter of personal taste or conscience (Romans 14:1 (NAS) after all one did not have to eat pork if they did not want to.
Paul did not have the authority to countermand God, so he should not be interpreted as trying to do that, and should not be followed instead of God even if that is what he was trying to do. God did not give his people any room to follow anyone who speaks against obeying any of His laws (Deuteronomy 4:2, 13:4-5).
While Paul said that circumcision has not value that what matters is obeying the commands of God (1 Corinthians 7:19), he also said that circumcision has much value in every way (Romans 3:1-2) and that circumcision conditionally has value if someone obeys the Mosaic Law (Romans 2:25), so the issue is not that circumcision has not value or great value, but that it has no inherent value as a special status, and its value is entirely derived from whether someone obeys the Mosaic Law. In Romans 2:26, the way to recognize that a Gentile has a circumcised heart is by their obedience to the Mosaic Law, which is the same way to tell for a Jew (Deuteronomy 10:12-16, 30:6), while the way to recognize that someone has an uncircumcised heart is by their refusal to obey it (Jeremiah 9:25-26, Acts 7:51-53).
The topic of Romans 14 stated in the first verse is in regard to how to handle disputable matters of opinion, not in regard to whether followers of God should follow God's commands, so nothing in the chapter should be interpreted as speaking against obeying God. Paul was not saying that we are free to commit murder, idolatry, theft, adultery, break the Sabbath, or disobey any of God's other commands just as as long as we are convinced in our own minds that it is ok, but rather that was only said in regard to things that are disputable matters of opinion. For example, God gave no command to fast twice a week, but that had become a common practice in the 1st century (Luke 18:12), so whether someone chooses to do that is a disputable matter of obedience, but God has commanded His people to refrain from eating unclean animals, so whether someone does that is a matter of obedience to God.
Romans 7 Paul is not saying he was PRESENTLY keeping the OT law. Romans 7:1-6 Paul points out it is sinful for the Christian to try and keep the NT gospel of Christ and the law of Moses at the same time, a spiritual adultery, like the adulteress woman keeping 2 husbands at the same time. Paul pointed out earlier in Romans one is justified by faith NOT by deeds of the OT law. Here in Rom 7 he shows the way for the Christian to serve Christ is to get out from serving the OT law that was a yoke of bondage in requiring flawless, perfect law keeping to be justified. Paul as a Christian struggles with sin and in the remainder of Rom 7 Paul showed himself as Saul, a non-Christian Jew struggling to meet the perfect, flawless demands the OT required. He loved the OT law and tried to keep it perfectly but would always fail. Paul contrasts his life back then as a non-Christian Jew under the law and condemend by that OT law for not keeping it perfectly to "NOW" being a Christian in Christ where there is no conedemnation Romans 8:1.
Sin is defined in the NT as the transgression of God's law (1 John 3:4), not as obedience to it. It completely absurd to interpret Romans 7:1-6 as Paul saying that it is sinful to follow Christ's example of obedience to God's law and that what God really wants from us is our disobedience. All throughout the Bible, God wanted His people to repent from their sins and to return to obedience to His law and never once was it the other way around. In Romans 7:22-23, Paul said that he delighted in obeying God's law, but contrasted it with a law of sin, which held him captive, so if Romans 7:4-6 were referring to God's law, then that would mean that Paul was speaking against obeying God, that he was speaking against obeying a law that he delighted in obeying, that he was saying the way to be united with Christ is by rejecting the way that he taught to be united with him, that Paul delighted in stirring up sinful passions in order to bear fruit unto death, and that he delighted in being held captive, which is all completely absurd, but rather it is the law of sin that he described as holding him captive. Furthermore, everything in Romans 6 is speaking in favor of obedience to God and against sin, not the other way around.
While Paul said in Roman 3:28 that we are justified by faith apart from works, he followed that up in verse 31 by saying that our faith does not abolish our need to obey God's law, but rather our faith upholds it, yet you are trying to use verse 28 to say the opposite.
The view that we have of the Mosaic Law matches the view that we have of the Lawgiver. For example, God is trustworthy, therefore His law is also trustworthy (Psalms 19:7), and a law that isn't trustworthy can't come from a God who is trustworthy, so to rely on the Mosaic Law is to rely on the Lawgiver. The Psalms express an extremely positive view of the Mosaic Law, such as with David repeatedly saying that he loved it an delighted in obeying it, which certainly matched his view of the Lawgiver, so if we consider the Psalms to be Scripture and to therefore express a correct view of the Mosaic Law, then we will share it, as Paul did (Romans 7:22), while view God's law as being bondage is expressing an extremely poor view of God and is incompatible with the view that the Psalms are Scripture.
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The OT law itself did require perfect flawless law keeping to be jsutified by it. One sin and a person was under the curse of that law (Galatians 3:10) for the OT law showed no mercy, but condemned. Because of this perfect, flawless law keeping required by the OT law of Moses, Paul says of the OT law
"And the law is not of faith: but, The man that doeth them shall live in them." Again, when it came to justification under the OT law faith did not matter, for what did matter is keeping the OT law perfectly. doing the law, Leviticus 18:5....do the law and live. Yet the Jew could not keep and live in the law perfectly therefore Paul says "no man is justified by the law in the sight of God" because again the Jew xould not keep it perfectly. But one is now under the NT justified by faith, Galatians 3:11. Therefore there is no reason for anyone today suggest people keep ANY of the OT law for keeping the OT law CANNOT justify anyone.
The Mosaic Law was never given as a means of earning our justification as a wage (Romans 4:4-5), so someone would not earn their justification even if they had managed to live in perfect obedience to it. That has always been a fundamental misunderstanding of why we should obey the Mosaic Law, which is why the NT repeatedly speaks against obeying for that reason, but that doesn't meant that we aren't obligated to obey it for the reasons for which it was given.
In Deuteronomy 11:26-32, the difference between being under God's blessing or His curse is based on whether we choose to follow God or chase after other gods, not based on whether or not we have perfect obedience. While everyone in the OT fell short of perfect obedience, everyone being under God's curse does not reflect the reality of what is recorded about those who served God, just those who chased after other gods. The law itself came with instructions for what to do when the people sinned, so perfect obedience was never a requirement. Repentance doesn't change the fact that we have fallen short of perfect obedience, so the fact that repentance has value means that we don't need perfect obedience. In Deuteronomy 30:11-20, it says that God's law is not too difficult to obey and that obedience brings life and a blessing while disobedience brings death and a curse, so choose life! So it was presented as a choice and as a possibility, not as the need for perfect obedience. Thinking that we are under a curse if we sin once would mean that God essentially gave the law with the goal of cursing His children, which is expressing an extremely poor opinion of God, when in reality it was given for our own good in order to bless us (Deuteronomy 6:24, 10:12-13).
In Matthew 23:23, Jesus said that faith is one of the weightier matters of the Mosaic Law, so the Mosaic Law is of faith. In Romans 3:27, Paul contrasted a law that was of works with a law that was of faith, so works of the law are of works, while he said in 3:31 that our faith upholds the Mosaic Law, so again the Mosaic Law is of faith and Paul contrasted the Mosaic Law with works of the law. In Galatians 3:10-12, Paul associated a quote from Habakkuk 2:4 with a quote from Leviticus 18:5, so the righteous who are living by faith are the same as those who are living in obedience to the Mosaic Law, while no one is justified before God by works of the law because they are not of faith in God. It does not follow that because we do not earn out justification by obeying God that we therefore aren't obligated to obey God for some other reason, such as faith.