Plato wrote the following: If the perfectly just man were to come into the world…“He will be scourged, racked, and bound. He will have his eyes burned out. And at last, after suffering every kind of evil, he will be impaled.” Plato regarded the Son of God as a “just man”. He knew enough about the nature of humankind to know that we would not run to embrace the perfect man. (“He came unto His own, but His own did not receive Him.”)

Why according to Plato was it better to act unjustly?
According to Plato it was better to act unjustly for a few reasons. Mainly an unjust person could receive more in life by taking things from others, thus making them more happy, therefore having a overall better experience in life. The only consequence of being unjust is if you are caught and then your reputation will change, (like how your criminal record will always follow you). Thus, if you always seem like you are a just person despite stealing goods from others you get the best of both worlds. It is also said that an unjust person is not necessarily evil, remember Robin Hood? He is unjust but you would consider him a good person right? He stole for the less fortunate and broke the law and without him those people would be worse off for themselves if Robin Hood was just. Therefore it can be seen that acting unjust could be better.

The natural laws are effective enough to never dissipate, they were originally created by man but then over time people realized they were good laws and came to believe they could be laws created by god. 

The origin of justice is when man recognized that certain principles are very beneficial to society and that there should be a clear moral compass of what is good and of what is bad so the people created their own laws to follow their moral values because they work to keep the peace. 

He believed we have laws because people know what is right and what is wrong so having laws is a beneficial concept to any society, and citizens recognized this so they codified their values into laws.