Michael Corleone to Frank Pentangeli

I was always glad that after my father died, this house didn't go to strangers, that it stayed in the family. This very room was my father's study. I used to come here many times while he was working. My father taught me alot of things in this room. Many things. It was in this very room that my father once said to me, 'Michael, to be strong for your family, there are many things a man must do. The most important thing to remember is this:
Keep your friends close, but your enemies closer.'

The Godfather Part II