Although I can get behind the other answer, I saw it in a different light.
Jaqen gives Arya three names to name, because she saved three men who were going to be taken by the Red God. Those three names she names are to settle this debt.
Jaqen's god primarily deals with death, and the claiming of lives.
If it were the other way around ("All men must serve" / "All men must die"), I would take it to be a statement about life itself.
But because it is inverted (dying before serving), I take this to mean that those men still serve (the many faced god) after death.