Thou shalt

It's interesting how morality, a way to live ones life, changed from its conception.
I suppose it's important to realise that it is a concept born of rational need, as society drew together and interpersonal rules and the values you placed on your fellow man developed.
The Greeks held the view that morality and ethics were of this world, a philosophical expression of thought which lived alongside the sciences being discovered and codified.
Mankind had a responsibility to consider his own life and improve upon it for no other reason than for the betterment of society and his fellow man. The gods that he acknowledged, were totems of the physical world and the things he felt he had no control over.  A God of war, a God of love a God of the sea and all its mysteries, these gods were not integrated with him but stayed apart and separate.
It was only from the stories which make up Genesis, Exodus, Leviticus, Deuteronomy, did the concept of an authoritarian God who was prescriptive and laid down the rules of behaviour for mankind, that religion came into its own.
Gods interaction with Abraham in the story of the burning bush and, much later, Gods revelation through Moses of the prescriptive Ten Commandments which were handed to mankind through Moses  and became the crucible of Christianity and the Muslim faith, where discretion was taken out of man's hands and became, "the will of God".  
In Christianity, what fundamentally altered from the Jewish adherence to the teachings of the Old Testament was that the "means", the attitude and the consideration one gave to the way one lived ones life was an "end" in its self, (much as in Buddhism).  In the Jewish teaching the "means" had only one end, "Gods acceptance".

 It is interesting to see the difference of emphasis in the teachings of Christ which come to us by the books of Mathew, Mark, Luke and John themselves written quite a while after the crucifixion.

Christ seems to have led by example and left no actual written record and so we are left with interpretation, consolidated by Paul who came on the scene even later to publish through his letters his distinctive entreaty to the believers to reach out and preach the word according to the stories of Christ's life and his message as interpreted by the New Testament
The fundamental difference between the prescriptive path followed by the Commandments of the Old Testament and the realisation of Christ that mankind is weak and that religion is a journey in which one endeavours to abide by the Commandments. That in the end you will be judged for effort as much as the success.