Here are some links giving you information re: the questions asked when we studied Galatians Chapter 1.
1. Why would God choose something as strange as circumsion as his covenant? Why on the 8th day? This is a lengthy but interesting article. If you would like to focus on the answer to the question, scroll down to the bottom where you'll find St. Thomas Aquinas' answers to our question.
2. What is the significance of Bar/Bat Mitzvah in the Jewish religion?
This is from a Jewish source:
Hope this helps. See you Friday!
Krishna Smith