Where did the teaching that we are not under law but under grace come from?

Les explains that the whole theme of this little letter to the Galatian church is that we're not under law, we're under grace. He emphasizes that this statement came straight from the lips of the Apostle Paul, first and foremost, and up until that time it was an unknown tenet. Even Peter for the most part had no comprehension of this great move of God to come away from Israel and the covenant promises and go out to the whole wide world, Jew or Gentile, with the gospel of the grace of God. Les notes that we don't know it until we get to Paul, and this is hard for many people to swallow. He also disagrees with those who say there is no difference between Peter's message and Paul's, calling the difference daylight and dark. He points to later in the chapter where there was a difference of opinion, and to Peter's second epistle, where Peter wrote that the things written by Paul are hard to be understood.