Judges and officers shall you appoint for yourself in all your gates...(Deuteronomy 16: 18).
Appoint for yourself: Appoint your conscience. A person should always judge himself first and his conscience should follow him in every step he takes.
בכל שעריך: The Siftei Kohen explains that our body is like a city with seven gates: two eyes, two ears, two nostrils and the mouth. A person should appoint internal judges to examine everything you hear, see and let out of your mouth.