Buddha himself came up with the five precepts as a way to help
his students that weren't monks to live a life that is peaceful and
full of happiness.
The actions that are avoided by keeping the five precepts are
actions that can lead to suffering. So, the precepts are a way of
protecting yourself and others from that suffering.
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Michael Corleone ordered the killing of the heads of the five
families to 'settle all family business'.