You're just not understanding the scriptures which Paul wrote above then. For they speak salvation by faith vs. the works of the Law. Yes Paul did speak against observing the law. Did you not read the scripture that I provided for you where Paul, speaking of the works of the law and considering those things as refuse?
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If anyone else thinks he has grounds for confidence in the flesh, I have more:
5circumcised on the eighth day, of the people of Israel, of the tribe of Benjamin; a Hebrew of Hebrews; as to the law, a Pharisee;
6as to zeal, persecuting the church; as to righteousness in the law, faultless.
7But whatever was gain to me I count as loss for the sake of Christ.
8More than that, I count all things as loss compared to the surpassing excellence of knowing Christ Jesus my Lord, for whom I have lost all things. I consider them rubbish, that I may gain Christ
9and be found in Him,
not having my own righteousness from the law, but that which is through faith in Christ, the righteousness from God on the basis of faith.
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So, in Philippians 3:4-6 Paul is speaking about his zeal for the law and everything related, namely, his being a Hebrews of Hebrews, from the tribe of Benjamin, a Pharisee of Pharisee's, etc., Of those things he then says that he counts them as 'rubbish' not trusting in his own righteousness (observance of the law and all things related) but to know Christ through faith, the righteousness from God based on faith. So how can you claim that Paul never preached against the Law or failed to observe it when he counts it all as rubbish?
When those so-called believing Pharisees were teaching "you must be circumcised and made to obey the law given to Moses," it brought sharp disagreement with Paul and Barnabas, i.e. they were not in agreement with it. Then they brought this before the counsel in Jerusalem and the following was concluded:
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"Then some men came down from Judea and were teaching the brothers, “Unless you are circumcised according to the custom of Moses, you cannot be saved.”
2And after engaging these men in sharp debate, Paul and Barnabas were appointed, along with some other believers, to go up to Jerusalem to see the apostles and elders about this question."
Sharp debate would mean that Paul and Barnabas were not in agreement with the Pharisees who were claiming that the Gentile believers must be circumcised and made to obey the law of Moses. Again, how can you say that Paul did not speak against the law, when in fact he is doing so in the scripture above?
But some believers from the party of the Pharisees stood up and declared, “
The Gentiles must be circumcised and required to obey the law of Moses.”
6So the apostles and elders met to look into this matter.
7After much discussion, Peter got up and said to them, “Brothers, you know that in the early days God made a choice among you that the Gentiles would hear from my lips the message of the gospel and believe.
8And God, who knows the heart, showed His approval by giving the Holy Spirit to them, just as He did to us.
9He made no distinction between us and them, for
He cleansed their hearts by faith.
10Now then, why do you test God by placing on the necks of the disciples a yoke that neither we nor our fathers have been able to bear?
11On the contrary, we believe it is through the grace of the Lord Jesus that we are saved, just as they are.”
In the scripture above, Peter is referring to when He was sent to the Cornelius' household, where while Peter was still speaking the gospel, the Holy Spirit fell on them all speaking in languages and prophesying. These are just a few examples and there many others that I previously listed regarding faith vs. the works of the Law.
Don't read these scriptures and ignore their meanings, but understand what is being said!