What was used to form the basic laws of many nations?

Answer 1

The Code of Hammurabi was the earliest set of laws. See Link.

In many Christian countries, the 10 commandments:

ONE: 'You shall have no other gods before Me.'

TWO: 'You shall not make for yourself a carved imagery likeness of anything that is in heaven above, or that is in the earth beneath, or that is in the water under the earth.'

THREE: 'You shall not take the name of the LORD your God in vain.'

FOUR: 'Remember the Sabbath day, to keep it holy.'

FIVE: 'Honor your father and your mother.'

SIX: 'You shall not murder.'

SEVEN: 'You shall not commit adultery.'

EIGHT: 'You shall not steal.'

NINE: 'You shall not bear false witness against your neighbor.'

TEN: 'You shall not covet your neighbor's house; you shall not covet your neighbor's wife, nor his male servant, nor his female servant, nor his ox, nor his donkey, nor anything that is your neighbor's.'

...but many of these are just basic obvious moral rules.