What does Romans 13:9 mean?
Paul has written in the previous verse that the person who loves another has fulfilled the law. Now he begins to explain what he meant by that statement.As an example of the entire law, Paul lists four of the Ten Commandments, those forbidding adultery, murder, stealing, and coveting. Paul then adds the statement "and any other command." This is the equivalent of the modern "etcetera," or "etc." He has in mind all the commands included in the law, especially those about human relationships.
All those commands can be summed up in the word "love" from the command in Leviticus 19:18, "You shall love your neighbor as yourself." As Paul will show in the following verse, you cannot love someone and murder them or cheat on them or steal from them or covet their belongings. In this way, if we will obey the command to love our neighbors, we will fulfill all the other commands by default.