Paul, as we all know, is the true founder of Christianity, understood as a new, separate religion from Judaism. Paul rejected the Torah and lived a law-free lifestyle, encouraging Gentile Christians to do the same, right?
That Paul advocated a law-free approach for Gentile believers seems clear, but what about Paul himself? Paul, after all, was not a Gentile. Did he indulge in duplicitous activity, pretending to be an observant Jew when in the company of Jews and pretending to be be liberated from the Torah in the company of Greeks? That's the standard explanation of 1 Corinthians 9:19-23.
But hang on! Is it a Christian thing to flip-flop depending on who you're trying to win an argument with? Imagine you've been convinced by the blighter into thinking it was hunky-dory to continue as an observant Jew while coming to Christ, then discovering you're labelled "weak in the faith" at best, and accused of clinging to traditions that have been made obsolete and cancel out genuine faith. Wouldn't you feel you'd been misled?
And how do you explain Paul's claim in 2 Corinthians 11:24 that he received thirty-nine lashes no less than five times from synagogue authorities. You had to be a self-identified Jew - not an ex-Jew - to fall under the authority of these Jewish authorities. Try that trick on anyone else and the Roman authorities would be seriously hosed off.
Then there's that Nazarite vow Paul takes - in the Temple no less - just before his arrest. He does it to convince his critics that he's dutiful in his (Jewish) religious observances. Did he have his fingers crossed behind his back at the time? This, remember, is the bloke who hauls Peter over the coals and calls him a hypocrite in Galatians.
Mark Nanos is a contemporary Jewish scholar of the New Testament who asks provocative questions like these. His discussion of 1 Corinthians 9 is well worth checking out.