What is encouraging is that the span from Acts 21-28 gives a great view of how Paul declared his own practice "under oath" and before both Jews and gentiles starting with clarification of his teaching for his fellow Messianic Jews.
Acts 21
24 take them and purify yourself along with them, and pay their expenses so that they may shave their heads; and all will know that there is nothing to the things which they have been told about you, but that you yourself also walk orderly, keeping the Law
Acts 24
14But this I confess to you, that according to the Way which they call a sect, so I worship the God of my fathers, believing all things which are written in the Law and in the Prophets
Acts 25
8 while he answered for himself, “Neither against the law of the Jews, nor against the temple, nor against Caesar have I offended in anything at all.;
Acts 26
Therefore, having obtained help from God, to this day I stand, witnessing both to small and great, saying no other things than those which the prophets and Moses said would come; 23 that the Christ would suffer, that He would be the first to rise from the dead, and would proclaim light to the Jewish people and to the Gentiles;
Acts 28
17 And it came to pass after three days that Paul called the leaders of the Jews together. So when they had come together, he said to them: Men and brethren, though I have done nothing against our people or the customs of our fathers, yet I was delivered as a prisoner from Jerusalem into the hands of the Romans,... I have called for you, to see you and speak with you, because for the hope of Israel I am bound with this chain.
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23 So when they had appointed him a day, many came to him at his lodging, to whom he explained and solemnly testified of the kingdom of God, persuading them concerning Jesus from both the Law of Moses and the Prophets, from morning till evening