The ninth commandment

16 "You shall not bear false witness against your neighbor.

-- Exodus 20.16

A simpler way to put this is "Don't lie." I've always told my daughters that lying is the worst thing they can do to someone. It's one thing to do something wrong but lying is like spitting in someone's face while you do it.

And don't try to be technically honest while trying to deceive people. You might fool some human beings in this world, but you'll never fool God.