One of the many things going on in this chapter is the bit where an angel (I’m guessing not Gabriel, otherwise Luke would have identified it as Gabriel) announces Jesus’ birth to the shepherds. I wanted to zero in on the angel’s announcement. He says, “I bring you good news of great joy which will be for all the people; for today in the city of David there has been born for you a Savior, who is Christ the Lord” (10-11). When Gabriel foretold the birth of John the Baptist to Zacharias, he didn’t even explicitly mention the Messiah, and when he visited Mary, his tone was overwhelmingly that of a messenger proclaiming the coming of a king. The emphasis was overwhelmingly on Jesus’ reign.
Paul’s got a two-pronged argument here for those among the Galatians who would want to hang onto the Jewish law and insist that it’s necessary for salvation. He starts with a contrast between law and faith, similar to his arguments in the first handful of chapters from Romans, then moves into one based on chronology. But before we get into all that, I just want to note: the Galatians are by and large not Jews themselves! But they’ve bought into this false gospel from diehard Jewish legalists that being a Christian means getting circumcised and getting your kosher on and keeping the Sabbath. Which, honestly, strikes me as a serious feat of persuasion, getting predominantly Greek Gentiles to adopt the restrictive legal code of a minority religious-ethnic group that enjoys no particular popularity in the Roman Empire.