Since every Christian is called to be a minister of reconciliation (2 Corinthians 5:17ff), it's good to think through how you might share with people in different situations. Here's a real situation with some made-up names. As a Christian, what would you say to help this person:
Amanda is an old friend from high school who knows that you are a pretty committed Christian. She is Jewish and identifies religion as being very important to her. She is married to Bill, who she explains is a devout Catholic. They are expecting a son in a few months, and are having a bit of a conflict in regards to whether to have their son undergo the Jewish tradition of a Bris, which is the ceremony of circumcision that takes place on the 8th day of the boy's life.
Bill is very opposed to performing the Bris, because he feels that it would be an indication that that they are committing to raise him as Jewish. Amanda doesn't understand why circumcision is a big deal, since it fulfills the covenant that was made with Abraham and is a part of the Old Testament which Christians embrace.
So what do you think about this situation? Should Bill allow his son to have a Bris? What would you say to Amanda with regard to why Christians don't perform a Bris for their newborn sons?