Galatians 2:1-2,7-14; Psalm 116(117); Luke 11:1-4
Paul is in todays part of his letter to the Galatians, making a case that certainly might apply in our lives today. Bear in mind that Cephas is St Peter, the rock on whom Jesus built his church. Paul meets Peter and gains his full approval for how he preaches the good news to the uncircumcised - that is the Gentile community in Turkey where he is writing to. The approach taken by Paul was to accept local customs and to not impose the ancient and carefully preserved customs of the Jews (for which the Circumcision is a symbol - what is ray at stake are all the rules, traditions and customs of the old way). But, when Peter meets such uncircumcised people he does not practice what he has agreed with Paul, and does insist on the full observance of Jewish ritual and laws.
The story of this disagreement is also told in Acts 15 - but there, the emphasis is on the gentiles to take care not to upset the Jews by flaunting their non-observance of the full rites and customs. The difference is due to the very different audiences the letter and the book of Acts were written for.
So right from the very beginning, within one lifetime of Christ, we christians have been arguing about the rights and wrongs of all sorts of things. But the fundamentals are what matter: Todays Gospel has Jesus answering our call to know how to pray, with perhaps the one truly universal prayer all Christians and indeed many non christians know by heart - the Our Father. Christs' response contains the truth we need to know and follow - our relationship with our God as our Father, is the one important thing. I am told that much of the Our Father exists in the Jewish prayer, the Kaddish.