Some books have a continuing impact on my life. The Mark of the Christian by Francis Schaeffer is a small book that I read and reread.
Francis Schaeffer commenting on John 13:33-35 wrote the following.
This passage reveals the mark that Jesus gives to label a Christian not just in one era or in one locality but at all times and all places until Jesus returns.
Notice that what he says here is not a description of a fact. It is a command which includes a condition: “A new command I give you: Love one another. As I have loved you, so you must love one another. By this all men will know that you are my disciples, if you love one another.” An if is involved. If you obey, you will wear the badge Christ gave. But since this is a command, it can be violated.
The point is that it is possible to be a Christian without showing the mark, but if we expect non-Christians to know that we are Christians, we must show the mark.
You can access the book at http://www.ccel.us/schaeffer.html
Peace and Joy!