How is it then that both Peter and Paul lived like gentiles when they were among the Galatians? Paul never encouraged anyone to continuing to follow the scruples of the Mosaic law. A wrong reading of Acts 21 would lead one to conclude that rigorously following the Mosaic law was still required for a certain segment of the Church, even today.
It is poor interpretive methodology to isolate a single passage from the rest of the Bible and think you have it right.
Not to jump in the middle, but TTR’s statement (of following certain aspects of the Law by Jewish Christians) is hardly taking text in isolation, and, in fact, continued observance of the Law by Jewish Christians(not Gentile Christians) was the accepted practice by most Jewish converts of the time, and today.
The entire “Judaizer” issue centered around the flip side of this; well-meaning Jewish Christians who were circumsizing gentiles and having them follow the Law. Such was incorrect, as gentiles were not under the Law of Moses, but rather under the Laws of Noah.
In that passage, Gentiles are instructed to continue the Law of Noah and Jews instructed to continue to follow the Laws of Moses -— for purposes of “not being a stumbling block” and general good practice.
Nothing at all to do with Salvation; everything with getting along in your community.